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I 



A MANUAL OF 
Experiments and Projects 
in 

PHYSICS 


H. CLYDE KRENERICK 

NORTH DIVISION HIGH SCHOOL 
MILWAUKEE, WISCONSIN 


D C. HEATH AND COMPANY 

BOSTON NEW YORK CHICAGO 

ATLANTA SAN FRANCISCO DALLAS 
LONDON 



» 




•» 


# • 




A MANUAL OF 
Experiments and Projects 
in 


PHYSICS 


H. CLYDE KRENERICK 

n 

NORTH DIVISION HIGH SCHOOL 
MILWAUKEE, WISCONSIN 


D. C. HEATH AND COMPANY 

BOSTON NEW YORK CHICAGO 

ATLANTA SAN FRANCISCO DALLAS 

LONDON 




Copyright, 1931, 

By H. Clyde Krenerick 


3 G 1 


« 

«• 



* * • 


©CIA 40723 


PRINTED IN THE UNITED STATES OF AMERICA 


flUG 12 1931 




PREFACE 


The distinction between this manual and the large number of 
manuals already published is that it is written to be used when there 
is perfect correlation between laboratory work and classroom discus¬ 
sion; when, if desired, the laboratory work precedes the lecture-room 
presentation. It is written not as a laboratory text, but to accom¬ 
pany a text and each experiment presupposes that the student is 
familiar with the content of some definite assignment. 

The author has for many years assigned the topic and the next 
day sent the student to the laboratory to test for himself the subject 
of his lesson before his interest and enthusiasm was cooled by class¬ 
room demonstration and discussion. 

The nature of the experiment and the apparatus has been modi¬ 
fied so that the great majority of students are able to complete the 
experiment and have their work accepted in one period of fifty 
minutes. 

For the exceptional student who finishes his experiment early in 
the period, there is an optional part, which is a continuation of 
some phase of the experiment or a problem applying the principle 
involved. 

When the laboratory work is to correlate perfectly with the class¬ 
room discussion and become an integral part of the teaching method, 
it is necessary that all students work on the same experiment. For 
best results it is desirable that they work individually on the large 
majority of experiments. The apparatus required for the experi¬ 
ments in Part I is comparatively inexpensive, and the consequent 
cost for sets of twenty-four in nearly all experiments is not pro¬ 
hibitive in the average school. A complete list of the apparatus 
needed for each experiment is given at the back of the manual. 

Mechanics, Sound, and Light are arranged for the first semester 
and Heat and Electricity for the second semester. This sequence 
of subjects is best if the projects in Part II are to be considered in 
a group. However no experiment or group of experiments is based 
on knowledge obtained in some previous experiment, consequently 
they may be performed in any desired order. 

There are many desirable experiments or tests where the appara¬ 
tus is of such a nature and cost that sets are impossible. Twenty-one 
such experiments or projects are given in Part II. These projects 

iii 


are of a practical nature, the principles of physics applied to practi¬ 
cal problems. 

The author’s method has been to set up the apparatus for the 
projects in Part II some five or six weeks before the close of the 
semester. They serve as a laboratory review of the semester’s 
work. Here the students work in groups of two, or individually if 
they wish, and perform as many as possible, making their own 
selections. 


TABLE OF CONTENTS 

PART I. EXPERIMENTS 

NUMBER PAGE 

1. English and Metric Units . 2 

2. Volume of Cylinder — Vernier Caliper. 4 

3. Volume of Sphere—Micrometer Screw. 6 

4. Density in English Units. 8 

5. Density in Metric Units. 10 

6. Levers and Moments. 12 

7. Parallel Forces. 14 

8. Center of Gravity. 16 

9. Pulleys . 18 

10. Inclined Plane. 20 

11. Screw — Automobile Jack. 22 

12. Horsepower — Prony Brake. 24 

13. Coefficient of Friction. 26 

14. Efficiency of Machine. 28 

15. Archimedes’ Principle. 30 

16. Specific Gravity. 32 

17. Open Manometer — Gas Pressure. 34 

18. Closed Manometer — Lung Pressure. 36 

19. Hooke’s Law. 38 

20. Tensile Strength . 40 

21. Composition of Forces. 42 

22. Simple Crane. 44 

23. Resolution of Forces. 46 

24. Accelerated Motion. 48 

25. Laws of the Pendulum. 50 

26. Acceleration of Gravity. 52 

27. Second Law of Motion. 54 

28. Wave Length by Resonance. 56 

29. Wave Length by Interference. 58 

30. Laws of Vibrating Strings. 60 

31. Plane Mirrors. 62 

32. Convex Cylindrical Mirror. 64 

33. Concave Cylindrical Mirror. 66 


v 




































NUMBER PAGE 

34. Spherical Mirrors. 68 

35. Index of Refraction of Water. 70 

36. Speed of Light in Glass. 72 

37. Refraction by Prisms. 74 

38. Lenses — Focal Length and Images. 76 

39. Coefficient of Linear Expansion. 78 

40. Specific Heat of Metals. 80 

41. Temperature of Gas Flame. 82 

42. Latent Heat of Snow. 84 

43. Latent Heat of Steam. 86 

44. Efficiency of Gas Heating. 88 

45. Magnetic Fields. 90 

46. Electromotive Forces. 92 

47. Resistance — Ammeter-voltmeter. 94 

48. Resistance — Wheatstone Bridge. 96 

49. Series Circuits. 98 

50. Parallel Circuits.100 

51. Battery Connections.102 

52. Terminal Voltage and Resistance of Cell.104 

53. Electromagnetism.106 

54. Electric Bell.108 

55. Telegraphy.109 

56. Electrolysis. 110 

57. Efficiency of Electric Heating.112 

58. Electromagnetic Induction. 114 

59. Study of Dynamos.116 

60. Study of Electric Motors.118 

61. Horsepower of Automobiles.120 

62. Power and Torque Curves.122 

63. Automobile Road Thrust.124 

64. Automobile Electric Circuits.126 

PART II. PROJECTS 

1. Efficiency of Gas Water-Heaters .130 

2. Efficiency of Gas Stove .132 

3. Efficiency of Different Kettles and Flames.134 

4. Pressure Cooker.136 

5. Efficiency of Electric Plate Stove .138 

6. Efficiency of Electric Grid Stove.140 

7. Efficiency of Electric Water Heater.142 

8. Efficiency of Electric Fireless Cooker .144 

9. Electric Lights — Cost per C.P. Hour.146 


vi 










































NUMBER PAGE 

10. Household Lamp Connections. 148 

11. Heat and Light Radiations of Lamps.150 

12. Gas Flatiron.152 

13. Electric Flatiron .154 

14. Horsepower and Efficiency of Electric Motor.156 

15. Horsepower and Efficiency of Water Motor.158 

16. Horsepower and Efficiency of Gas Engine.160 

17. Study of Automobile Engine.162 

18. Study of Automobile Chassis.164 

19. Automobile Gear Ratios.166 

20. Automobile Electric System.168 

21. Factors Determining H.P. of Automobile Engines . . . 170 

Appendix A — Tables.172 

Appendix B — List of Apparatus.181 


vii 
















EXPERIMENTS 


PHYSICS MANUAL 


Experiment 1 — ENGLISH AND METRIC UNITS 

(a) Linear Measurements 

Measure the length of a rectangular block in both inches 
and centimeters and record in tabular form as indicated be¬ 
low. To use the meter stick properly, place the edge against 
the surface to be measured so that the eye is in line with 
the graduations. When measuring in the English units 
estimate to the thirty-second of an inch and record in decimal 
form expressed to the second place. 

From the results obtained, compute the number of centi¬ 
meters in one inch. Express to the second decimal place. 
Consult your text or manual and record the correct values. 

(b) Surface Measurements 

Measure the width of the block in both inches and centi¬ 
meters and compute the area of the top of the block in square 
inches and in square centimeters. 

From the results obtained, compute the number of square 
centimeters in one square inch. 

(c) Volume Measurements 

Measure the thickness of the block and determine its 
volume in cubic inches and in cubic centimeters. 

Compute the number of cubic centimeters in one cubic 
inch. 


2 



Tabulation 


System of Units 

English 

Metric 

Length of block 

.... in. 

.... cm. 

No. of cm. in one inch 


.... cm. 

Correct equivalent 


.... cm. 

Width of block 

.... in. 

.... cm. 

Surface of top of block 

.... sq. in. 

. . .. sq. cm. 

No. of sq. cm. in a sq. in. 


.. . . sq. cm. 

Correct equivalent 


. . . . sq. cm. 

Thickness of block 

.... in. 

.... cm. 

Volume of block 

. .. . cu. in. 

. . . . cu. cm. 

No. of cu. cm. in a cu. in. 


.. . . cu. cm. 

Correct equivalent 


.. . . cu. cm. 


Optional 

Compute the number of kilometers in a mile. The square 
decameter is called an are and the square hectometer is called 
a hectare. They are used in measuring land. Determine the 
number of ares in an acre. Use the correct equivalents. 
One acre contains 160 square rods. 


3 




Experiment 2 — VOLUME OF CYLINDER — VERNIER 
CALIPER 


The vernier caliper consists essentially of two scales, one 
of which slides along the other. The shorter or sliding scale 
is called the vernier; the longer the fixed scale. The object 
to be measured is placed between the jaws which are so 
made that, when they are in contact, the zero of the vernier 
is opposite the zero of the fixed scale. Hence measuring with 
the caliper is in reality finding the distance between the two 
zero lines. 

Determine the magnitude of the smallest division of the 
fixed scale. Compare the sliding scale with the fixed scale 
and determine the length of the vernier. Compute the mag¬ 
nitude of each division of the vernier. 

The difference in length between one division of the fixed 
scale and one of the vernier is called the “least count.” 
It determines to what part or fraction of the fixed scale 
division the measurement can be taken. 

Set the caliper so that the reading or distance between 
the jaws is exactly 2 cm.; 2.3 cm.; 2.37 cm. When set for 
the last reading, take the caliper to your instructor for veri¬ 
fication. 

Measure accurately the diameter, circumference, and length 
of a brass cylinder. To measure the circumference wrap a 
piece of writing paper closely around the cylinder and make 
a pinhole through the overlapping edges. Remove the paper 
and measure the circumference by placing the sharp-pointed 
jaws in the two pinholes. 

Compute the ratio of the circumference to the diameter, 
the area of the end of the cylinder, and the volume of the 
cylinder. 


4 



Smallest division of fixed scale .... 

Length of the vernier .... 

Smallest division of vernier .... 

Least count of caliper .... 

Diameter of cylinder .... 

Length of cylinder .... 

Circumference of cylinder .... 

Circumference -5- diameter .... 

Area of end of cylinder .... 

Volume of cylinder 

Optional 

In a like manner determine the first six records in the 
tabulation using the English scale on the caliper. Have 
your reading for the length of the cylinder verified by taking 
your caliper to the instructor. 


5 







Experiment 3 —VOLUME OF SPHERE — MICROME¬ 
TER SCREW 


The micrometer screw is an instrument for measuring small 
dimensions with great accuracy. The graduation on the 
outer cap is called the circular scale; that on the hub, the 
linear scale. The instrument should be held in the left hand 
and the screw adjusted by placing the thumb and finger of 
the right hand on the ratchet head, which is the outer and 
smaller milled head. 

When closing the jaws or when placing objects between the 
jaws, always move the screw by turning the ratchet head, and 
continue to turn it until two clicks are heard. In this way 
the pressure will be always the same. 

Turn the head or cap through exactly four revolutions 
and note how far the edge of the circular scale has moved 
along the linear scale. Record the distance the screw moves 
during one revolution as the pitch of the screw. 

Count the number of divisions in the circular scale. How 
far does the screw move lengthwise when the cap is moved 
through one division of the circular scale? Record this as 
the least count of the instrument. 

Set the instrument so that it will read successively: 
5.00 mm., 5.01, 5.15, 5.50, 5.55, 5.75, mm. Now set it to 
read 11.675 mm., and submit it to the instructor for exam¬ 
ination. 

Close the instrument and note if the zero line of the circu¬ 
lar scale coincides with the line running lengthwise of the 
hub. If not, record the reading as a zero reading and make 
proper allowance for it in all readings. If the zero reading 
is to be added, it should be recorded as positive; if to be 
subtracted, negative. 

Determine the diameter of the wire (B. & S. gauge, 
No. 20) at three different points along the wire and record 
the average. In a like manner determine the diameter of 
the sphere and compute its volume. 


6 


Tabulation 

Pitch of the screw .... 

No. of divisions in circular scale .... 

Least count of the micrometer .... 

Zero reading of micrometer .... 

Reading with wire No. 20 .... 

Diameter of wire No. 20 .... 

Reading with sphere .... 

Diameter of sphere .... 

Volume of sphere in cu. cm. _ 

Optional 

Change the diameter of the wire into inches and express 
as so many thousandths of an inch or mils. Consult copper- 
wire table and find the diameter in mils of copper wire 
B. & S. gauge, No. 20. Such a table may be found in your 
text under the subject of Electrical Resistance, or in the 
Appendix of Manual. 


7 












Experiment 4 — DENSITY — ENGLISH UNITS 


Density of Wood 

Measure the three dimensions of the block of wood using 
the vernier caliper. Change the fractions of the inch to. 
the decimal form and express to the second place. 

To weigh the block use the spring balance (18 oz. capacity). 
Hang the balance from a spike clamped to a vertical support 
rod. Before reading a spring balance, give the mass to be 
weighed a slight up-and-down vibration two or three times 
and note if the pointer comes to rest at the same position. 
Note that by estimating to a half division, the balance can 
be read to the tenth of an ounce. 

Determine the volume of the block and compute the den¬ 
sity of wood in ounces per cubic inch and in pounds per cubic 
inch. 


Density of Water 

Measure the inside diameter of the cylindrical vessel using 
the inside jaws of the caliper. To measure the depth of 
the vessel use the extension or depth gauge of the caliper. 

Fill the vessel level-full of water and weigh on the spring 
balance. 

Determine the volume of the vessel and compute the 
density of water in ounces per cubic inch and in pounds per 
cubic inch. 


8 



Tabulation 


Wood 


Length of block 

. in. 

Width of block 

. in. 

Thickness of block 

. in. 

Weight of block 

. oz. 

Volume of block 

. cu. in. 

Density of wood 

. oz. per cu. in. 

Density of wood .. .. 

. lb. per cu. in. 

Water 

Diameter of vessel 

in. 

Depth of vessel 

in. 

Weight of water 

oz. 

Volume of water 

cu. in. 

Density of water 

oz. per cu. in. 

Density of water . . .. 

lb. per cu. in. 


Optional 

Weigh five fluid ounces of water and compute the volume 
in cubic inches of a fluid ounce. 

Weigh a half of a measuring cup of water and compute the 
volume in cubic inches of a measuring cup. 

9 











Experiment 5 — DENSITY — METRIC UNITS 


Density of Wood 

Measure the three dimensions of the block of wood using 
the vernier caliper. Record readings in centimeters. 

To weigh the block use the platform balance. When 
using the balance, observe the following rules: 

(a) Move the slider on the graduated horizontal bar so 
that the left edge is on the zero line and note if the pointer 
comes to rest at the central line of the scale or, better, if it 
swings the same number of divisions on each side of the 
central line. 

(i b ) Always place the object to be weighed on the left- 
hand pan. 

(c) In placing known weights on the right-hand pan, try 
the weights in consecutive order beginning with a large 
weight. Do not use weights smaller than the five gram. 

(i d ) Make the final balance by moving the slider to the 
right. Read the grams and tenths of grams on the bar and 
add to the weight on the pan. 

(e) Never leave the weights or object weighed on the pans 
for any length of time after the weight is recorded. 

Determine the volume of the block and compute the den¬ 
sity of wood in grams per cubic centimeter. 


Density of Water 

Measure the inside diameter of the cylindrical vessel using 
the inside jaws of the caliper. To measure the depth of 
the vessel, use the extension or depth gauge of the caliper. 

Fill the vessel level-full of water and weigh on the platform 
balance. 

Determine the volume of the vessel and compute the 
density of water in grams per cubic centimeter and in kilo¬ 
grams per liter. 


10 



Tabulation 

Wood 


Length of block 

.... cm. 

Width of block 

.... cm. 

Thickness of block 

.... cm. 

Weight of block 

-gm. 

Volume of block 

.... cu. cm. 

Density of wood 

.... gm. per cu. cm. 


Water 

Diameter of vessel 

.... cm. 

Depth of vessel 

.... cm. 

Weight of water 

-gm. 

Volume of water 

.... cu. cm. 

Density of water 

.... gm. per cu. cm. 

Density of water 

.... kgm. per liter 


Optional 

Determine the weight of a level teaspoonful, dessert¬ 
spoonful, and tablespoonful of dry salt. Compute the num¬ 
ber of teaspoons in a dessertspoon and in a tablespoon. 

When weighing a substance like salt, place it on a filter 
paper. A second filter paper should be placed on the weight 
pan. 


11 











Experiment 6 —LEVERS AND MOMENTS 


First Test: Fulcrum between Forces 

Place a wire nail through hole in center of a half-meter 
stick and clamp to a vertical support at a point six or eight 
inches above the table. 

Determine and record in ounces the weight of the two 
masses. Use a 64 oz. capacity spring balance and two and 
four pound masses. 

By means of a loop of thread suspend the smaller mass 
near the right-hand end of the stick and suspend the larger 
mass on the left at a point at which it will exactly balance 
the mass on the right. 

Record the distances and weights and compute the mo¬ 
ment of each force. The perpendicular distance from the 
line of action of a force to the fulcrum is called the arm of 
the force. 

Second Test: Weight between Fulcrum and Pull 

Attach the spring balance to the hole near one end of the 
stick and suspend the larger mass at some point between the 
balance and the fulcrum. Read the balance when the stick 
is horizontal. 

Record the forces and their arms and compute the moment 
of each force. The weight lifted or the force exerted by a 
machine is called the resistance and the pull or the force 
applied to a machine is called the effort. 


Third Test: Effort between Fulcrum and Resistance 

Suspend the smaller mass at a point near one end of the 
stick and hook the balance in the hole nearly midway between 
the fulcrum and the end of the stick. Read the balance when 
the stick is horizontal. Record all forces and compute the 
moment of each force. 


12 



Tabulation 

First Test: Weight of large mass - 

Weight of small mass .... 

Arm of large force .... 

Arm of small force .... 

Moment of large force .... 

Moment of small force .... 

Second Test: Weight used (resistance) .... 

Balance reading (effort) .... 

Resistance arm .... 

Effort arm .... 

Moment of resistance .... 

Moment of effort .... 

Third Test: Weight used •••• 

Balance reading .... 

Resistance arm 
Effort arm 

Moment of resistance - 

Moment of effort .... 

Optional 

Repeat the second test suspending both masses, at two 
different points, between the balance and the fulcrum. Re¬ 
cord forces and arms on a diagram and compute the mo¬ 
ments of all forces involved. What relation of moments can 
be expressed? 

13 








Experiment 7 — PARALLEL FORCES 


Part A 

Weigh three different size masses (one, two and four 
pound) to the nearest ounce. Use a spring balance of 64 oz. 
capacity. 

Clamp a small rod at right angles to the vertical support 
rod. Place two spring balances on the bar and suspend a 
half-meter stick from the hooks in such a manner that the 
balances will be parallel and some distance apart. 

In order to eliminate the weight of the bar, read each 
balance and record as the “zero reading.” These readings 
are to be subtracted from subsequent readings of the balances 
when measuring forces. 

Suspend the three masses from the stick at such positions 
that the stick will be exactly horizontal. Record the forces 
upward at the balances. What relation is seen between the 
total upward and the total downward forces? 


Part B 

With the apparatus as balanced in A, select any point 
you wish along the stick as the fulcrum. Measure the dis¬ 
tance from the point of application of each force to the point 
selected as the fulcrum and record as the arm of that force. 

Compute the moment of each force. If the force tends to 
produce clockwise rotation around the selected point, re¬ 
cord it as a positive moment. If counterclockwise, record 
it as a negative moment. 

What general principles can be stated concerning the ful¬ 
crum and moments of parallel forces? 


14 



Tabulation 
Part A 


Weight of large mass 

. ... oz. 


Weight of medium mass 

.... oz. 


Weight of small mass 

.. . . oz. 


Upward fo^je, right balance 

.... oz. 


Upward force, left balance 

.... oz. 


Total downward force 

. ... oz. 


Total upward force 

.. .. oz. 


Part 

B 



Point selected as fulcrum 



Arm of large mass 

.... cm. 


Arm of medium mass 

.... cm. 


Arm of small mass 

.... cm. 


Arm of right balance 

.... cm. 


Arm of left balance 

.... cm. 


Moment of large mass 


... . oz. 

cm. 

Moment of medium mass 


. .. . oz. 

cm. 

Moment of small mass 

-f- or — 

► . . . . oz. 

cm. 

Moment of right balance 


. . . . oz. 

cm. 

Moment of left balance 


.. . . oz. 

cm. 

Sum of positive moments 

. .. . oz. 

cm. 

Sum of negative moments 

. .. . oz. 

cm. 


Optional 

A bridge 60 feet long weighs 20 tons and has its center of 
gravity at the center. A six-ton truck stands with its center 
of gravity 15 feet from the north end. Find the total weight 
supported at each end of the bridge. 

15 







Experiment 8—CENTER OF GRAVITY 


Part I 

Weigh the half-meter stick on a platform balance to the 
nearest tenth of a gram. (As most of the sticks weigh be¬ 
tween 70 and 80 grams, a quick determination can be made 
by placing 70 grams on the right-hand pan and using the 
beam and rider to complete the balance.) 

Find the center of mass or the center of gravity by bal¬ 
ancing it on a prism. The stick may be considered balanced 
when it will remain with either end down. Read to the 
millimeter and record as the location of the center of gravity. 

Place a 50-gram weight on the stick so that its center will 
be over a line one centimeter from the end, and without the 
use of any other weights place the stick on the prism in 
such a position that it will be in equilibrium. The edge of 
the prism should be at right angles to the stick. 

Measure carefully and record the distance from the ful¬ 
crum to the center of the weight and from the fulcrum to the 
center of gravity of the stick. Compute the moment of the 
weight. If the weight of the whole stick were to act as a 
single force with its point of application at the center of 
gravity, compute its moment and record as the moment of 
the stick. 

What relation is found between the moment of the weight 
and the moment of the stick? What definition does this 
relation suggest for the center of gravity? 


Part II 

Repeat the experiment using a brass cylinder of unknown 
weight in place of the 50-gram mass. From the relation 
of moments discovered in Part I, compute the weight of 
the cylinder. Determine the correct weight of the cylinder 
by using the platform balance. Record the number of the 
cylinder. 


16 



Tabulation 


Part I 


Location of center of gravity 

.... cm. 

Weight used 

-gm. 

Distance (weight to fulcrum) 

.... cm. 

Weight of stick 

-gm. 

Distance (fulcrum to center of gravity) 

.... cm. 

Moment of weight 

.... gm. cm. 

Moment of stick 

.... gm. cm. 

Part II 


Number of cylinder 


Distance (cylinder to fulcrum) 

.... cm. 

Distance (fulcrum to center of gravity) 

.... cm. 

Moment of stick 

.... gm. cm. 

Moment of cylinder 

.... gm. cm. 

Weight of cylinder (computed) 

... .‘gm. 

Weight of cylinder (weighed) 

-gm. 

Optional 



Place the 20-gram weight one centimeter from one end of 
the stick and the 50-gram weight one centimeter from the 
other end. With the weights thus placed balance the stick 
on the prism and show that the moments are still equal. 
Draw a diagram and record t>n the diagram the forces and 
distances. 


17 













Experiment 9 — PULLEYS 


A spring balance is made to read correctly in a vertical 
position with the hook downward. When the balance is 
used inverted, a correction must be made. To determine 
the correction place the hooks of two spring balances to¬ 
gether and clamp to the support rod so that one balance 
will be inverted and. the other in correct position. Adjust 
a clamp so that the balances will read near center of scale. 
Determine what correction must be made on the inverted 
balance to make reading correct, or same as the upper bal¬ 
ance. 



(a) . Arrange the apparatus as shown in A. The lower 
clamp should be so adjusted that the weight will be lifted 
from the table. Record the corrected balance reading as the 
pull (P) necessary to support the weight (W). 

Note and record as (N) the number of sections of the cord 
that are helping to support W; that is, the number of cords 
passing to and from the weight. Determine the weight of 
the iron mass and record as W. Calculate the ratio of W to 
P and express it as a quotient to the second decimal place. 

( b ) Repeat all of (a) with apparatus arranged as in B. 
Note that the pulley or movable block here forms a part of 
the weight and should be included in W. 

(c) Repeat all of ( b ) with ajjparatus as in C. 

(d) Repeat all of (6) with apparatus as in D. 


18 


























Tabulation 

Part P W W -t- P N 

A . 

B . 

C . 

D . 

What statement can be obtained from a comparison of 
the last two columns? How can the mechanical advantage 
of a system of pulleys be determined? 

Optional 

Determine by diagram the mechanical advantage of two 
fixed and three movable pulleys. Also for three fixed and 
two movable pulleys. 


19 





Experiment 10 — INCLINED PLANE 


Weigh the car or roller on the platform balance to the 
nearest gram and record as the resistance force. As the in¬ 
clined plane is a machine used to raise an object to a different 
level, the weight of the object moved up the incline is the 
force exerted by the machine against gravity. 

Weigh the pan and cord to the nearest gram. Set the plane 
at an angle of 25 degrees and in such a position that the pan 
suspended by the cord over the pulley can rise and fall with¬ 
out touching the edge of the table. Adjust the pulley so 
that the cord is parallel to the plane. 

Place the least weight in the pan that will cause the car, 
once gently started, to continue rolling slowly and uniformly 
up the incline. Add to this weight the weight of the pan 
and record as the force necessary to pull the car up the 
incline, or the theoretical effort plus friction. 

To eliminate friction, take off weights until the car will, 
when gently started, continue to roll slowly and uniformly 
down the incline. The weight of pan and load is now the 
force necessary to hold the car on the plane aided by friction. 
Record as effort minus friction. The average of these two 
forces would be the effort if there were no friction. 

Measure along the incline from the table top to the high¬ 
est edge of the plane and record as the length of the inclined 
plane. Measure the perpendicular distance from this edge 
to the table and record as the height of the plane. 

Compute the ratios of the resistance to the effort and the 
length to the height. Express to the second decimal place. 

Compute the work done by the effort to roll the car to 
the top of the incline (input), and the work done by the re¬ 
sistance against gravity (output). Record the unit in which 
the work is measured. 


20 



Tabulation 

Resistance force (R) .... 

Weight of pan .... \ 

Effort plus friction .... 

Effort minus friction .... 

Effort force (E) .... 

Length of inclined plane .... 

Height of inclined plane .... 

Ratio: Resistance to Effort .... 

Ratio: Length to Height .... 

Input (name of unit) .... 

Output (name of unit) .... 

State what you have proved to be the mechanical advan¬ 
tage of an inclined plane. 

Optional 

Determine the grade of the incline used in the experiment. 

Note: A Second Method — The board or incline shown in 
Experiment 14 is used as the inclined plane. For the object to be 
rolled up the incline use a two-pound mass in a four-wheel car. 
Use a spring balance to determine the weight of the car and load 

and the force (effort plus friction) necessary to roll the car uni¬ 

formly up the incline. Let the car roll uniformly down the incline 
to determine the effort minus friction, 

21 








Experiment 11 — SCREW — AUTOMOBILE JACK 


Determine the theoretical mechanical advantage of the 
screw. When measuring the radius of the circle through 
which the effort applied to the screw acts, measure from the 
center of the axis to a point on the end of the handle where 
the hook of the spring balance is attached. To determine 
the pitch, measure the distance of ten threads. 

Place a spike in the hole at the end of the lever and clamp 
to a vertical support rod. On the other end of the lever place 
a large spring balance (30 lb. capacity) with its hook at¬ 
tached to a block clamped underneath the edge of the table. 
Place the jack underneath the lever at a point about one- 
fifth as far from the fulcrum as the large spring balance. 
Place a small cylinder between the top of the jack and the 
lever so that the point of application will be definite. Oper¬ 
ate the jack until the spring balance reads about twenty- 
five or thirty pounds. 

Attach a smaller spring balance (64 oz. capacity) at the 
end of the handle and determine the force, at right angles 
to the handle, necessary to lift the lever. Get a series of 
five or six readings of this force by watching the balance and 
note the reading when the handle is moving. Record the 
average as the effort on the screw. 

The record for the large balance should be the average 
of its readings taken at the beginning and at the end of the 
series of trials for the effort. 

Consider the spike as the fulcrum of the lever. The mo¬ 
ment of the force of the large spring balance is then equal 
to the moment of the force exerted upward on the lever by 
the jack. Compute the force exerted by the jack and record 
as the resistance of the jack. From the resistance and effort 
obtained, compute the actual mechanical advantage of the 
jack. 

Compute the work done by the effort applied to the 
screw in one rotation of the screw (input). Also the work 
done by the jack in one rotation (output). Compute the 
efficiency of the screw. 


22 



Tabulation 

Length of handle (radius) .... 

Pitch of screw .... 

Mechanical advantage of screw .... 

Reading of small balance (effort) .... 

Length of balance arm .... 

Length of jack arm .... 

Reading of large balance .... 

Force exerted by jack (resistance) .... 

Mechanical advantage (actual) .... 

Work done by effort (input) .... 

Work done by resistance (output) .... 

Efficiency of automobile jack .... 

Optional 

Count the number of teeth on the two gear wheels. What 
effect do these gears have on the theoretical mechanical 
advantage of the jack? Explain. If the gear wheel on the 
screw has twice the number of teeth of the other, what then 
would be the mechanical advantage of the jack? 


23 







Experiment 12 — HORSEPOWER — PRONY BRAKE 


The horsepower of any producer may be determined by 
a device known as the Prony brake, one form of which is 
constructed by placing a belt around the drive wheel and 
attaching a spring balance to each end of the belt. 

As the wheel rotates the difference between the two bal¬ 
ances will give the force exerted by the wheel on the belt. 
This force will be acting each minute through a distance 
equal to the circumference of the wheel timos the number 
of revolutions per minute. From the force and distance 
obtained the horsepower can be computed. 

Place a short (2 in.) vertical support rod in a receptacle 
near one end of the table and use as the axle of the large 
grooved wheel. Place a large washer on the support rod 
between the table and wheel. (A tripod base clamped to 
the table may be used in place of the receptacle in the table 
top.) 

Attach the two ends of a short piece of rope to two spring 
balances of 30 pounds capacity. Place the rope in the groove 
of the wheel and attach the two spring balances to table 
clamps on the edge of the table. By moving the clamps 
along the edge of the table, a varying tension can be placed 
on the rope. 

The student making a test of his power should determine 
before the test the greatest pull of the balances that he can 
maintain for one minute with a constant speed of rotation. 
The speed of rotation is not to exceed one revolution per 
second. Only one hand is to be used throughout a test. 

The student rotating the wheel should count the number 
of revolutions made during the minute test. A second stu¬ 
dent should keep time and record the average readings of 
the two balances during the test. 

Make a second trial using the other hand. Each student 
should make the tests and record only the data of his own 
trials. 


24 



Tabulation 

Arm Tested Right Left 

Reading of first balance .... .... 

Reading of second balance .... .... 

Force (pull on rope) .... .... 

Revolutions per minute .... .... 

Circumference of wheel .... .... 

Distance (feet per minute) .... .... 

Work (foot pounds per minute) .... - 

Total work done .... 

Horsepower .... 


Optional 

The “Spirit of St. Louis” was equipped with a 200 horse¬ 
power engine. Colonel Lindbergh in his famous trip flew 
3610 miles in 33.5 hours. What was the force exerted against 
the air by the propeller? 


25 














Experiment 13 — COEFFICIENT OF FRICTION 


Before starting the experiment see that the surface of the 
board and the surfaces of the block are thoroughly cleaned 
with sandpaper. 


Part A — Coefficient 

Friction is measured by measuring the force necessary to 
overcome it. Place the smaller mass on the block and attach 
the hook of the spring balance to the hook on the block. 
Determine the force necessary to start the block (starting 
friction) and the force necessary to keep the block in slow 
uniform motion over the top of the board (sliding friction). 
Several trials should be made before recording any results. 
Record what seems to be the normal or average reading. 

For a second test, place the larger mass on the block. For 
a third test, use both masses. In each test compute the 
coefficient of both starting and sliding friction. Express to 
third decimal place. 

Part B — Area of Contact 

Using the block and the larger mass determine the force 
of sliding friction when the block is sliding on its largest 
surface and when it is turned up and sliding on its edge. 


26 



Tabulation 
Part A — Coefficient. 

Trials 12 3 

Weight of block . 

Weight on block . 

Total pressure . 

Force of friction (starting) . 

“ “ “ (sliding) . 

Coefficient of friction (starting) . 

“ “ “ (sliding) . 

Part B — Area of Contact 
Contact Surface Side Edge 

Weight of block • • • • 

Weight on block • • • • 

Total pressure • • • • - 

Force of friction - - 

Coefficient of friction • • • • 

Optional 

What load can a horse working at the rate of one-half 
horsepower, draw along a level highway at the rate of three 
miles an hour, if the coefficient of friction between the sled 
runners and ice covered road is 0.02? 


27 
























Experiment 14 — EFFICIENCY OF MACHINE 


Raise one end of board to form an inclined plane. This 
can be done by placing one end of nail in the clamp and the 
other end in hole on edge of board. Adjust the clamp until 
the lower edge of upper end of board is just six inches above 
the table. 

Measure the length of the inclined plane or the distance 
from the lower edge to the table along the lower surface of the 
board. Considering the lower surface of the board as the 
surface of the inclined plane, measure the base or the distance 
along the table from the vertex of the plane to a point di¬ 
rectly underneath the upper end of the plane. 

With the spring balance determine the force necessary to 
pull the block and iron mass slowly and uniformly up the 
incline. To prevent the iron mass from slipping, place its 
ring in the hole of the block. 

Make two more tests with the lower edge of the raised 
end of the board eight and ten inches respectively above the 
table. Measure the force necessary to overcome friction 
when the surface is horizontaL 

Compute the work done by the machine against gravity 
(output). Compute the work you did on the machine when 
sliding the mass the length of the incline (input). To com¬ 
pute the work done against friction multiply the force of the 
friction, when the surface is horizontal, by the base. 


28 



Tabulation 


Height of Inclined Plane 

Six Eight Ten In. 


Length of inclined plane 

.in. 


Base of inclined plane 

.in. 


Pull on the incline 

.oz. 


Force of friction (horizontal) 

.oz. 


Weight of block and mass 

.oz. 


Output, total mass X height 

.in. 

oz. 

Input, pull X length 

.in. 

oz. 

Work done against friction 

.in. 

oz. 

Input minus output 

.in. 

oz. 

Efficiency of inclined plane 




Optional 

Compute the actual efficiency of the inclined plane in 
Experiment 10. The input should now be determined when 
the car is moving up the incline. 


29 
















Experiment 15 — ARCHIMEDES’ PRINCIPLE 


Part A — Sinking Object 

Determine the buoyant force (apparent loss in weight), 
on a sinking block when submerged in water. When weigh¬ 
ing an object submerged in water, first take the balance 
reading with the pan submerged. 

To determine the weight of the water displaced by the 
block, use an overflow can. To use the overflow vessel 
properly, place it on a block and pour in water until it is 
nearly full. Let the excess water flow out of the overflow 
spout into a catch vessel. Do not disturb the can or touch 
the end of the overflow spout at any time. Lower the block 
slowly and carefully into the can and catch the water it dis¬ 
places in an empty vessel. 


Part B — Floating Object 

Use the wood cylinder and the overflow can to determine 
the relation between the weight of a floating object in air and 
the weight of the water displaced by the object when floating. 
Care must be taken when lowering the cylinder into the 
can, that it does not go below its normal floating level. 

I. State Archimedes’ principle as applied to a sinking 
object. Explain from your data whether you have proved 
the principle. 

II. State Archimedes’ principle as applied to a floating 
object. Explain whether your results prove the principle. 


30 



Tabulation 
Part A 


Weight of block in air . ... oz. 

Weight of block in water -oz. 

Buoyant force • • • • 02 • 

Weight of catch vessel • • • • oz. 


Weight of catch vessel and water .... oz. 

Weight of displaced water .. .. oz. 

Part B 

Weight of cylinder in air .. .. oz. 

Weight of catch vessel • • • • oz. 

Weight of catch vessel and water -oz. 

Weight of displaced water . . . • oz. 

Optional 

A cubical box, three feet in each dimension, floats in water 
with two-thirds of its volume submerged. When a boy steps 
on the box it sinks three inches deeper in the water. Find 
the weight of the boy. 


31 








Experiment 16 — SPECIFIC GRAVITY 


Part A — Sinking Solids 

Determine the specific gravity of three of the following 
substances: coal, brick, marble, stone. In obtaining the 
weight of the object when submerged in water, first obtain 
the reading of the balance when the pan is submerged. 


Part B — Floating Solids 

Determine the specific gravity of the wood cylinder. To 
find the weight of an equal volume of water use the overflow 
can. To entirely submerge the cylinder, press it just below 
the surface with point of pencil. 


32 



Tabulation 
Part A 

Material Coal Brick Etc. 

Weight in air . 

Weight in water . 

Weight of equal vol. of water . 

Specific gravity . 

Part B 

Weight of wood cylinder . 

Weight of catch vessel . 

Weight of vessel and water . 

Weight of equal vol. of water . 

Specific gravity of wood . 

Optional 

Determine the specific gravity of a saturated solution of 
salt by weighing a piece of coal in air, then in the solution 
and then in water. 

Weight of coal in air . 

Weight of coal in solution . 

Weight of coal in water . 

Specific gravity of salt solution . 

33 



















Experiment 17 — OPEN MANOMETER 


Gas Pressure 

Fill the U-tube or open manometer until the level of the 
water is at the midpoint of the longer or vertical tube. Clamp 
the manometer in a vertical position. The clamp should be 
placed where the rubber tube overlaps the glass tube. Not 
much pressure at the clamp will then be necessary to hold 
the tube firmly. 

Connect the manometer to the gas-cock and turn on the 
gas very slowly. Measure the final difference in levels and 
record as the manometer reading. Compute the pressure of 
the gas in pounds per square inch. 

Read the barometer and compute the pressure of the at¬ 
mosphere in pounds per square inch. Determine the pres¬ 
sure absolute of the illuminating gas. 


34 



Tabulation 


Manometer reading 
Gas pressure 
Barometer reading 
Atmospheric pressure 
Gas pressure absolute 


.... in. 

. ... lb. per sq. in. 
.... in. 

. ... lb. per sq. in. 
. ... lb. per sq. in. 


Optional 


Take all readings in the metric system and determine the 
following: 


Manometer reading 
Gas pressure 
Barometer reading 
Atmospheric pressure 
Gas pressure absolute 


.... cm. 

.... gm. per sq. cm. 
.... cm. 

.. .. gm. per sq. cm. 
. .. . gm. per sq. cm. 


35 












Experiment 18 —CLOSED MANOMETER 


Read the barometer in inches and compute the atmospheric 
pressure in pounds per square inch. Record it as the initial 
pressure (P) or pressure on the enclosed air. 

Place water in the U-shaped glass tube so that, when held 
in the vertical position with closed end upward, the water will 
be at the same level in each tube and about two inches 
above the lower point of the tube. This can be done by 
pouring slowly a small quantity of water in the tube and then 
inverting the tube in such a manner that some of the water 
will pass around the bend into the closed end. 

Repeat the process until the water is about two inches 
high in the tube. Then hold the tube vertically with closed 
end up and pour in water until the levels are the same. 

Slip the open end of the tube about one inch into the rub¬ 
ber tubing and clamp in a vertical position. Be sure to 
place the clamp where the rubber tubing overlaps the glass 
tube. 

Measure in inches the length of the enclosed air column 
and record as the initial volume of air (V). 

Blow through the rubber tube and see how high you can 
force the water in the tube. Do not place the tube in the 
mouth. Place the tube in your closed fist and press your 
lips against the thumb and forefinger. Record the length 
of the resulting column of air as the resulting volume (v). 

From the initial pressure (P), the initial volume (V), and 
the resulting volume (v) compute the resulting pressure on 
the enclosed air. (Boyle’s Law.) 

The pressure from the lungs is not only compressing the 
air in the tube, but it is supporting the column of water in 
the closed tube. From the difference of levels compute this 
extra pressure. 

Record the total pressure as the pressure absolute. From 
the atmospheric pressure and the pressure absolute com¬ 
pute the lung pressure. 


36 



Tabulation 


Barometer reading 
Pressure on air, P 
Volume of air, V 
Resulting volume, v 
Resulting pressure, p 
Dif. of water levels 
Pres, of water column 
Pressure absolute 
Lung pressure 


. ... in. 

.... lb. per sq. in. 
.... in. sections 
. . . . in. sections 
. ... lb. per sq. in. 
. ... in. 

. ... lb. per sq. in. 
. ... lb. per sq. in. 
.... lb. per sq. in. 


Optional 

Repeat the experiment and record all readings in the met¬ 
ric system. Determine the lung pressure in grams per square 
centimeter. 


37 















Experiment 19 — HOOKE’S LAW 

Clamp the meter stick to the vertical support rod so that 
it will be horizontal and about one foot above the top of the 
table. See that the rod is rigid in the receptacle. 

Suspend the pan ten centimeters from the outer end of 
the meter stick. Hold a ruler in a vertical position and 
record in millimeters the exact distance from the table to 
the upper edge of the end of the stick as the zero reading. 

Place a 50-gram mass in the pan and again record the 
distance to the table. Repeat using the following masses: 
100, 150, 200, 250, 300, 350, 400 grams. Note and record 
the zero reading each time before placing a new mass on the 
pan. 

From your data compute the total bend produced by each 
weight or force. Also determine the ratio of the total bend 
to the force producing it in each trial. Express the ratio as 
a quotient to the second decimal place. 

What terms may be applied to the weight in the pan and 
to the bend or deflection produced? 

From the last column what statement can be made con¬ 
cerning the relation of deflection and weight? 

If the zero reading remains constant what does it signify? 


38 





Tabulation 

Weight 

Zero 

Reading 

in Pan 

Reading 

with Wt. 

50 gm. 
100 gm. 
150 gm. 
200 gm. 
250 gm. 
300 gm. 
350 gm. 
400 gm. 




Total 

Bend 


Ratio 


Bend 


Wt. 


Optional 

Using weights and deflections as coordinates, plot a curve 
showing the relation between the two. If coordinate or 
cross-section paper is not used, carefully rule a portion of 
one page of your notebook. 


39 



















Experiment 20 —TENSILE STRENGTH 


Fasten the ring of a large spring balance, 30 lb. capacity, 
near the edge of the table by means of a clamp. 

Cut a piece of copper wire No. 26, ten or twelve inches 
long. Caution: When cutting wire from a spool, to prevent 
the wire from unwinding and getting tangled, unwrap the 
end of the wire from the tack, unwind from the spool the 
length of wire needed, wrap once around the tack and then 
cut from the free end. 

Fasten one end of the wire firmly to the hook of the spring 
balance and the other end to a large spike. 

Two students should now work together, one to pull on 
the wire and the other to read the balance. The force of the 
pull should be increased very slowly so that the balance can 
be read at all times and the exact position of the pointer 
noted when the break occurs. 

In a like manner determine the breaking strength of a 
brass wire No. 32 and an iron wire No. 32. 

With a micrometer screw measure the diameter of each 
wire. Change the reading to inches and compute the cross- 
section area of the wire in square inches. 

From the force necessary to break the wire and the cross- 
section area, compute the tensile strength or the force neces¬ 
sary to break a wire one square inch in cross-section. 


40 



Tabulation 

Material in Wire Copper Brass Iron 

Gauge number of wire .... .... .... 

Zero reading of screw .... .... .... 

Diameter in millimeters .... .... .... 

Diameter in inches .... .... .... 

Cross-section in sq. in. .... .... .... 

Reading of balance .... .... .... 

Tensile strength .... .... .... 


Optional 

The Brooklyn Bridge is supported by four cables. Each 
cable is made up of 6300 steel wires, No. 7 gauge. The ten¬ 
sile strength of steel is 300,000 pounds per square inch. Com¬ 
pute the total breaking strength and express in tons. 


















Experiment 21 — COMPOSITION OF FORCES 


Connect the three balances as shown in the diagram. 
Balances A and B are connected to hooks at center of table, 
balance C to the block clamped to the edge of the table. Ad¬ 
just clamp and cords so that the balances will read between 
50 and 60 ounces. It is better not to have any two balances 



Place the open notebook on the table so that the center 
of the right-hand page will be under the junction of the cords. 
Draw lines that will represent the projection of the three cords 
on the page. Record near each line the tension or force on 
the cord. 

Represent the junction of the cords by 0. Let one milli¬ 
meter represent one ounce of force and lay off from 0 on each 
of the three lines a distance that will represent the magnitude 
of the force. Call these distances OA, OB, and 0(7. 

With any two of these lines as sides complete a parallelo¬ 
gram by using ruler and compass. Draw the diagonal from 0, 
measure its length, and record near it the magnitude of force 
it represents. 


42 







Tabulation 

Reading of balance A .... 

Reading of balance B .... 

Reading of balance C .... 

Length of side ( ) .... 

Length of side ( ) .... 

Length of diagonal OD .... 

Magnitude of resultant .... 

Magnitude of equilibrant .... 

If two of the forces were replaced by a single force that 
would have the same result, it would need to be equal and 
in opposite direction to the third force. If the force found 
by the diagonal is equal to the third force, what does the ex¬ 
periment prove? 


Optional 

Will the pull on the hammock hooks be increased or de¬ 
creased if they are put farther apart at the same height, the 
person in the hammock being consequently higher from the 
ground? Prove your answer by means of diagrams. 


43 











Experiment 22 — SIMPLE CRANE 

A good illustration of the resolution of a force is found in 
the simple crane or when a weight is hung out on a bracket 
from a pole. The beam is spoken of as the “boom” and the 
connection from the outer end of the boom to a higher point 
on the pole as the “tie.” 

The weight, a single vertical force, is resolved into two 
effective component forces: One is a tension in the tie rope, 
the other a thrust of the boom against the pole. 



Part I — Components Determined by Experiment 

Weigh the iron mass in ounces. Use the half-meter stick as 
the boom and connect to the support rod by placing the nail 
through the large hole. Before attaching the tie rope and the 
weight to the end of the boom, find the pull downward on 
the outer end of the boom due to its own weight. Add this 
to the weight of the iron mass. 

Attach the tie rope and the weight to the outer end of the 
boom. Adjust the upper clamp until the boom is horizontal. 
Bead the balance in ounces and record as the tie tension. 
To obtain the thrust of the boom against the support rod, 
hook a second spring balance to the screw eye in the end of 
the boom and pull outward until the stick just leaves the 
nail. This condition can be easily detected if that end of the 
stick rests lightly in the other hand. 

Part II — Components Determined by 
Parallelogram of Forces 

Measure with the protractor the angle between the boom 
and the tie rope. On the left-hand page of the notebook 

44 










draw three lines that will represent the directions of the three 
forces; weight, tie, and boom thrust outward. 

Extend the weight line vertically upward a distance to 
represent the weight. Let two millimeters represent one 
ounce of force. With this line as a diagonal, complete the 
parallelogram. Measure the sides representing the tie and 
thrust force and express in ounces. 



Tabulation 


Weight on end of boom .... oz. 

Tie tension by experiment .... oz. 

Boom thrust by experiment .... oz. 

Angle between tie and boom .... degrees 

Angle between boom and weight line .... degrees 
Length of diagonal .... mm. 

Length of tie side • • • • mm. 

Length of thrust side .... mm. 

Tie tension by construction .... oz. 

Boom thrust by construction ... . oz. 


Optional 

Raise the upper clamp on the support rod so that the boom 
is about 30 degrees to the horizontal and make a second test 
and parallelogram. 


45 













Experiment 23 — RESOLUTION OF FORCES 


When a body rests on an inclined plane, its weight which 
is a vertical force is resolved into two effective component 
forces. One of these effects is pressure on the plane, hence 
a force perpendicular to the plane. The other tends to pro¬ 
duce motion down the plane, hence a force parallel to the 
plane. 

If the plane is placed at Such an angle that the tendency 
to slide is just balanced by the force of friction, then by 
definition the ratio of the parallel force (friction) to the per¬ 
pendicular force (pressure) is the coefficient of friction. 



By similar triangles it will be seen that the friction force 
is to the pressure force as the height of the inclined plane is 
to the base. The coefficient of friction can therefore be de¬ 
termined by dividing the height by the base. 

Part I — Coefficient of Friction by Definition 

Weigh the block and iron mass in ounces. Place them on 
the board when in a horizontal position and find the force of 
sliding friction as in a previous experiment. Compute the 
coefficient of friction. 

Part II —Coefficient of Friction by Resolution of 
Forces 

Raise and clamp the board in such a position that the 
block and iron mass will just slide down with uniform motion 
if the board is constantly tapped lightly with the finger. 
The angle of the plane is now called the limiting angle of 
friction. Considering the lower surface of the board as the 
length of the inclined plane, measure the height and base and 
compute the coefficient of friction. 

46 








Tabulation 


Weight of block and iron . . . . oz. 

Force of sliding friction .... oz. 

Coefficient of friction .... 

Height of inclined plane .... in. 

Base of inclined plane .... in. 

Ratio of height to base .... 


Optional 

Coefficient of Friction by Construction of Parallelogram 

By means of a protractor measure the limiting angle of 
friction. Construct a right-angle parallelogram of forces by 
using the total weight as the diagonal and the angle of the 
plane as the angle between diagonal and one side. (Let two 
millimeters represent one ounce of force.) Determine the 
magnitude of the two forces represented by the sides of the 
parallelogram. Compute the coefficient of friction. Record 
lengths and magnitude of forces represented on the drawing. 


47 













Experiment 24 — ACCELERATED MOTION 


Place the acceleration apparatus or grooved plank on the table 
in a horizontal position with the grooved surface upward. Release 
the steel ball at the edge of the groove and observe that it rolls 
from one side to the other, like the movement of a pendulum, in 
equal periods of time. 

Raise one end of the plank 10 or 20 centimeters from the table. 
Release the ball at the center of the upper end of the groove and 
observe that it rolls down with increasing speed. Since the force 
causing the ball to roll is a constant component of gravity, it must 
roll with uniformly accelerated motion. 

While the plank is inclined, release the ball at the edge of the 
upper end. It should be released when placed against the upper 
surface of the guide so that it will not start to roll down the incline 
until it has reached the center of the groove. Observe in this trial 
that it has a combination of the first two motions and that the side 
movement may be used as a means of determining how far the ball 
rolls down the incline in equal periods of time. 

Wipe the grooved surface with a damp cloth and then rub 
it thoroughly dry. Cover the groove with a thin and uni¬ 
form sifting of lycopodium dust. Raise the end of the plank 
by means of blocks, 20 centimeters above the table. Care¬ 
fully release the ball at the edge above the guide. Blow away 
the powder very carefully and the dust showing the path of 
the rolling ball will remain on the plank. Place the meter 
stick on its edge in the groove so that its metric surface will 
be over the exact center of the groove. Record the total 
distance the ball rolled at the end of each period. Com¬ 
pute and record the distance rolled each individual period. 

Compute the speed of the ball at the end of each period by 
the formula: average speed = one-half of the initial speed 
(zero) plus the final speed (X); or, final speed = two times 
the average speed. To find the average speed during any 
number of periods, divide the total distance that the ball rolls 
by the number of periods. 

Determine the acceleration or increase in speed acquired 
during each period of time. 

Compute the ratio of the speed at the end of each period 
to the time. What simple relation seems to exist between 


48 


this ratio and the acceleration? Express as a formula for 
speed or velocity. 

Compute the ratio of the total distance at the end of each 
period of time to the square of the time. Obtain the average 
acceleration and the average ratio. What simple relation 
seems to exist between the acceleration and the ratio of the 
distance to the square of the time? Express as a formula. 
Transpose and obtain a formula for distance in terms of ac¬ 
celeration and time. 



Tabulation 

Number of the Period (Time) I II HI W 

Total distance at end of period . 

Distance rolled each period .*. 

Speed at end of each period . 

Acceleration in each period . 

Ratio (speed -s- time) . 

Ratio (distance 4- square of time) . 

Average acceleration 

Average of ratios (distance -f- sq. of time) 

Optional 

Compute by means of formulas the speed at the end of the 
tenth period and the total distance the ball would have rolled 
at the end of the tenth period. 


49 


























Experiment 25 — LAWS OF THE PENDULUM 

Fasten one end of a wax thread to the iron ball and suspend 
it in such a way that you have a pendulum exactly 36 centi¬ 
meters long, measuring from the center of the ball to the 
point of suspension. This can best be done by determining 
the radius of the ball with the caliper and obtaining the re¬ 
quired distance from the top of the ball to the point of sus¬ 
pension. 

If a regular pendulum suspension clamp is used, the cord 
should be placed between the clamp bar and the small side 
plate at the center binding post. Turn the milled head screw 
tight and the cord is firmly held. 

Set the pendulum swinging through an arc of ten centi¬ 
meters and count the number of single vibrations in one and 
a half minutes. To do this one student should keep record 
of the time while the others count the vibrations. The time¬ 
keeper holds the pendulum five centimeters to one side of 
the position of rest and releases it at some particular second. 
The students counting should be warned one second or more 
before the close of the period. 

Repeat using a pendulum of 81 centimeters in length. Use 
the same ball and the same arc. 

For a third test use the 81-centimeter pendulum with 
double the arc and determine the number of vibrations in the 
same length of time. 

For a fourth test use a wood ball in place of the iron ball. 
Use a length of 81 centimeters and an arc of ten centimeters. 

Compute the period or time of one vibration for each 
pendulum. 


50 


Tabulation 


Material 

Length 

Arc 

Time No. of Vib. Period 

Iron 

36 cm. 

10 cm. 

90 sec. .... .... 

Iron 

81 cm. 

10 Cm. 

90 sec. .... .... 

Iron 

81 cm. 

20 cm. 

90 sec. .... - 

Wood 

81 cm. 

10 cm. 

90 sec. .... .... 


I. State the effect of material and length of arc on the 
time of one vibration. 

II. State the exact variation discovered between the 
lengths and the periods of the different pendulums. 

III. State the exact variation discovered between the 
lengths and the number of vibrations of the pendulums. 


Optional 

By means of the relation between the length and the period 
discovered in the experiment, compute the length of a pen¬ 
dulum that would vibrate once a second. 


51 


Experiment 26 — ACCELERATION OF GRAVITY 

In this experiment all students at a table are to work in 
a group: one student keeping record of the time and the 
others counting the number of vibrations. 

Suspend a pendulum from a hook in the ceiling over a 
point near one end of the table. To measure the length of 
the pendulum, slip the ring on the end of the steel tape meas¬ 
ure over the hook in the ceiling and measure distance to the 
top of the iron mass or bob. To this distance add one-half 
of the vertical diameter or length of the iron mass. Notice 
that the small units on the measuring tape are tenths and 
hundredths of the foot. 

Draw a short chalk line on the table directly under the 
center of the bob and parallel to the side of the table. Set 
the pendulum swinging through an arc of about 20 inches at 
right angles to the chalk line and parallel to the end of the 
table. 

The timekeeper should take a position at the end of the 
table and, when ready to begin the test, start the stop watch 
at the exact instant that the pendulum passes over the chalk 
line in its movement from the timekeeper’s right to left. 
After the pendulum has vibrated for about ten minutes, give a 
warning signal and stop the stop watch as the bob passes 
over the chalk line going in the same direction (right to left). 
Record the time or duration of the test. 

The students counting should record a mark at each pas¬ 
sage of the pendulum over the chalk line from the same direc¬ 
tion (complete vibrations). Determine the number of single 
vibrations between the starting and stopping of the watch. 

Compute the period or time of a single vibration to the 
third decimal place. Substitute the square of the period 
obtained, the length of the pendulum, and the square of 
3.1416 in the pendulum formula and compute the accelera¬ 
tion of a falling object at your latitude and elevation. 


52 


Tabulation 


Distance from hook to bob . ft. 

Diameter or thickness of bob . ft. 

Length of pendulum . ft. 

Duration of test seconds 

Number of complete vibrations . 

Number of single vibrations . 

Time of a single vibration seconds 

Square of 3.1416 . 

Acceleration of gravity . 

Optional 

With the acceleration obtained, compute, by means of the 
pendulum formula, the length in inches of a pendulum that 
will vibrate once a second. 


53 











Experiment 27 — SECOND LAW OF MOTION 

The force of gravity acting on an object on an inclined 
plane is resolved into two forces. One of these component 
forces is the force causing the object to roll down the incline. 
The magnitude of this force can be determined by the prim 
ciple of the parallelogram of forces. 

In the diagram the line RW represents the force of gravity 
or weight and the line FR represents the force producing ac¬ 
celeration or motion down the incline. The triangles ABC 
and WRF are similar. Hence the force producing accelera¬ 
tion has the same relation to the weight of the object as the 
height of the plane has to its length. 

Weigh the ball to the nearest tenth of a gram. By means 
of blocks raise one end of the acceleration apparatus, or 
grooved plank, 20 centimeters above the table. Record the 
length and the height of the incline. Compute the magnitude 
of the force causing the ball to roll down the incline. 

Wipe the groove with a damp cloth and rub it thoroughly 
dry. Sift on the groove a thin and uniform layer of lyco¬ 
podium powder. Carefully release the ball at the edge of 
the groove just above the guide. Blow away the powder so 
that the track of the rolling ball will be seen by the powder 
which remains. 

Place the meter stick with its metric edge down the center 
of the groove and measure in centimeters the distance the 
ball rolled down the plank during the first four oscillations 
to the side or the first four equal periods of time. From these 
results determine the increase in distance passed over in each 
period of time and record the average as the acceleration. 

Raise the end of the plank 35 centimeters above the table. 
Record the length and height of the incline and compute the 
force producing acceleration. Determine as before the ac¬ 
celeration produced in the rolling ball by the new force. 

Express the relation or ratio of the two accelerations pro¬ 
duced. Also the ratio of the two forces producing accelera¬ 
tion. Record the ratios in decimal form to the second place. 
State the relation of the ratios discovered in the form of a 
law. 


54 



Tabulation 


Test Number I II 

Weight of ball .... .... 

Height of incline .... _ 

Length of incline .... .... 

Force producing acceleration .... .... 

Distance — First period .... .... 

Distance — Second period .... .... 

Distance — Third period .... .... 

Distance — Fourth period .... .... 

Acceleration (average) .... 

Ratio of accelerations .... 

Ratio of accelerating forces .... 

Optional 

If the force producing acceleration was the weight of the 
object, or if the angle of the incline was 90 degrees and the ob¬ 
ject fell, compute from your results its acceleration or the 
acceleration of a falling object. With a stop watch determine 
the period or time of one oscillation of the ball. Change 
the acceleration obtained (centimeters per “period,” per 
“ period ”) to centimeter per second, per second. If your 
result is not the true acceleration of a falling object, explain 
the cause of the error. 


55 













Experiment 28 — WAVE LENGTH BY RESONANCE 


Push a pencil into the rubber stopper and use as a tuning- 
fork hammer. Nearly fill the jar with water and clamp the 
tube in a vertical position so that its lower end will be near 
the water surface. 

If two students work together, one should set the fork 
in vibration and hold it as near as possible, without striking, 
to the upper end of the tube. The other should raise the jar 
of water, and note the level of water in the tube when the 
greatest reinforcement of the sound is produced. Place the 
rubber band on the tube at this level. Make several trials, 
readjusting the band if necessary, until sure that it is prop¬ 
erly placed. 

Measure the distance from the rubber band to the end of 
the tube. Change the position of the band and exchange 
work. Record the average of your results as the length of 
the air column. 

Experiment has shown that the length of a resonating air 
column is affected by the diameter of the tube. The correc¬ 
tion is made by adding .4 of the diameter to the length. 

Compute the wave length of the sound produced by the 
fork. From the frequency, indicated on the fork, and the 
wave length, calculate the speed of the sound. This would 
be the speed at the temperature of the air in the tube or the 
temperature of the water. Determine this temperature and 
compute the speed of sound at zero degrees Centigrade. 


56 



Tabulation 


Frequency of Fork . 

Length of air column .in. 

Diameter of air column .in. 

Corrected air column .in. 

Wave length .ft. 

Calculated speed of sound ft./sec. 

Temperature in tube degrees 

Temperature correction .ft. 

Computed speed at zero C. ft./sec. 

Correct speed at zero C. ft./sec. 


Optional 

Find by experiment the wave length of the sound produced 
by a fork of unknown frequency. Compute the correct speed 
of sound at the room temperature, and determine the fre¬ 
quency of the fork. 


57 



















Experiment 29 — WAVE LENGTH BY INTERFERENCE 


Connect a funnel to the main branch of a Y-tube with a 
short piece of heavy-wall rubber tubing. On a second Y-tube 
place a heavy-wall tube about 30 inches long. Place the Y- 
tubes, where the rubber overlaps, in universal clamps on two 
vertical support rods. Connect the upper prongs of the Y- 
tubes with a tube 12 inches long and the lower prongs with a 
tube 25 inches long. See that the tubes are resting loosely in 
the clamps. 

It is evident that sound waves entering the funnel will 
divide at the first Y-tube and unite at the second. If one 
branch is one-half a wave length longer than the other 
branch, the condensation of one wave and the rarefaction 
of the other wave will reach the single tube at the same time 
and little or no sound will be heard. 

One student should hold the end of the tube at his ear. 
For sanitary reasons, the end of the tube should be'held in 
the closed hand with the finger and thumb pressing against 
the ear. A second student should hold the vibrating fork 
(512 vibrations) before the funnel. The fork should be set 
into vibration by plucking. While the fork is vibrating, 
close the longer branch by pinching the tube and note the 
change in the loudness of the sound. 

Replace the longer branch with a tube 29.5 inches long and 
repeat the test. For the final test use the tube for the longer 
branch that best produces the least sound when both tubes 
are open, or the greatest contrast when one tube is closed 
and opened. Make final adjustments by sliding the tubings 
farther on or off of the forks of the Y-tubes. 

Measure carefully the length of each branch and determine 
the wave length of the sound produced by the fork. Make a 
second trial using a fork of 384 vibrations. 

Determine the temperature of the room and compute the 
velocity of sound at room temperature. From the formula 
expressing the relation between velocity, frequency, and wave 
length, compute the wave length of the sound produced by 
each fork. 


58 



Tabulation 

Frequency of Fork 512 384 

Length of long branch .... .... 

Length of short branch .... .... 

Wave length by experiment .... .... 

Temperature of room .... .... 

Velocity of sound at room temperature .... .... 

Wave length by formula .... .... 

Optional 

Disconnect the branches from the system and connect the 
heavy-wall tube directly to the funnel. While one student is 
listening at the end of the tube, the other should hold the 
vibrating fork (384 vibrations) in a vertical position near 
the funnel and slowly turn it on its axis one-fourth of a 
revolution. Describe and explain the result. 


59 















Experiment 30 — LAWS OF VIBRATING STRINGS 

Law of Length 

Cut a piece of steel piano wire No. 24 about 100 centi¬ 
meters long. Fasten one end of wire firmly to an iron ring 
and the other end to a small washer. Place the iron ring on 
a table clamp fastened to the edge of table and the washer 
on the hook of a 30-lb. capacity spring balance also clamped 
to the table. 

Place two triangular blocks or bridges under the wire and 
move the spring balance until the wire is under a tension of 
nine kilograms. 

Place the bridges at such a distance apart that the wire 
will be in unison with a C (256 vibrations) tuning fork. Set 
the tuning fork in vibration with a hammer made by placing 
a rubber stopper on the end of a lead pencil. See that the 
tension is correct before recording the length or distance be¬ 
tween the bridges. 

If you are not musically inclined, the string may be tuned 
by finding a point at which few or no beats are produced when 
both string and fork are vibrating. 

With the same tension determine, by moving the bridges, 
the length of wire that will produce G (384 vibrations). 
Compute the ratio of the frequencies and the inverse ratio of 
the lengths. Compute ratios to the second decimal. 


Law of Tension 

With the same length of wire as obtained with the G tun¬ 
ing fork, vary the tension until the wire produces C (256 
vibrations). Compute the ratio of the frequencies and the 
ratio of the square roots of the tensions. 

State each law proved in the experiment. 


60 



Tabulation 
Law of Length 

No. of Wire Frequency Tension Length 

24 256 9 kg. 

24 384 9 kg. - 

Ratio of frequencies .... 

Ratio of lengths (inverse) .... 

Law of Tension 

No. of Wire Frequency Tension Length 

24 384 9 kg. - 

24 256 

Ratio of frequencies 

Ratio of square roots of tensions .... 

Optional 

Use steel piano wire No. 26 and a tension of nine kilo¬ 
grams. Move the bridges and determine the length of wire 
that will produce C (256 vibrations). With the law of length 
compute what the frequency of the No. 26 wire would be if 
the length remained the same as that of the No. 24 wire when 
its tension was nine kilograms and its frequency 256. 

Compute the ratio of the frequencies of the two wires if 
their lengths were the same. With a micrometer screw 
measure the diameter of each wire. Compute inverse ratio 
of diameters. 


No. of Wire 

Frequency 

Tension 

Length 

Diameter 

24 

256 

9 kg. 



26 

256 

9 kg. 



26 


9 kg. 




Ratio of frequencies (lengths constant) 
Ratio of diameters (inverse) 


61 




Experiment 31 — PLANE MIRRORS 


Draw a line MN across the center of a right-hand page of 
your notebook. Place the mirror in a vertical position with 
the edge of its silvered surface exactly above the line MN. 
The mirror may be held in position by means of two blocks. 

In front of the mirror draw a line AB about three inches 
long, with the end A about three inches and the end B about 
two inches from the line MN. 

Set a pin in the point A and draw two lines along which its 
image can be seen. This can best be done by placing a ruler 
on the page and, sighting along one edge, point it in such a 
direction that a line drawn along its edge, if extended back 
of the mirror, would pass through the image of the pin. 
Since the image can be seen in each of these lines, it must be 
at their intersection. Better results will be obtained the far¬ 
ther apart these two lines are taken. 



/ \ 

i \ 


Place the pin at B and in a similar manner draw two sight 
lines toward its image. 

Remove the mirror and extend the first two lines until they 
meet at a point C. Mark the point of intersection of the 
second pair of lines D. Draw the line CD. Also the lines 
AC and BD. 

Measure the distance of each point, .A, B, C, and D, from 
the mirror or the line MN. 


62 











Tabulation 

Length of line A B .... 

Length of line CD .... 

Distance of A from mirror .... 

Distance of C from mirror .... 

Distance of B from mirror .... 

Distance of D from mirror .... 

What does the line CD represent and how does it compare 
in length with AB ? 

From these results what may be stated concerning the 
size and location of an image in a plane mirror? 

Optional 

Draw a line MN near one edge of a page of your notebook. 
Place the mirror on the line as before. Set a pin about three 
inches from the line MN and near one side of the page. 

Near the other side of the page draw a line AB along which 
the image of the pin can be seen, using ruler as before. Re¬ 
move the mirror and extend the line AB to the line MN. 
Draw a line from the pin point P to the point I where AB 
and MN intersect. 

What do the lines AI and PI now represent? Erect a per¬ 
pendicular DI to the line MN at the point I. By means of 
a protractor measure the angles AID and PID. What do 
these angles represent and what law has been proved? 


63 








Experiment 32 —CONVEX CYLINDRICAL MIRROR 

Part I — Focal Length 

Place the mirror in a vertical position near the center of 
the right-hand page of your notebook and with a sharp pencil 
draw a line along the base of the concave surface. 

Remove the mirror and determine by construction the 
mid-point of the curve. Mark it V (vertex). From V draw 
chords to each end of the curve. 

At the mid-point of each of these chords construct a per¬ 
pendicular and extend them until they meet at a point C 
(center of curvature). 

Measure and record on your drawing the radius of curva¬ 
ture and the focal length of the mirror. 

Part II — Images 

Place the mirror near the center of a second page and draw 
a line along the base of the convex side. Remove the mirror 
and draw the principal axis in dotted line. 

At a distance of one and a half times the focal length in 
front of the convex side of the mirror, draw a line AB four 
centimeters long at right angles to the axis. Place a pin at A 
and replace the mirror. 

By means of a ruler draw two lines (one on each side of the 
pin) that if extended would appear to pass through the image 
of the pin. Stand the pin at B and draw, as before, two lines 
toward its image. 

Remove the mirror and extend each set of lines until they 
intersect at points a and b. Draw the line ah, the image of 
the line AB. Connect A with the points where the sight 
lines strike the mirror. Show by arrows the direction of the 
rays of light as they leave A and after reflection. Connect 
B in a like manner. Describe the image as to size (larger 
or smaller than the object); form (erect or inverted); kind 
(real or virtual). 


64 


Tabulation 


Radius of curvature 
Focal length of mirror 
Size of image 
Form of image 
Kind of image 


Optional 

In the second diagram measure the length of the image 
and its distance from the mirror. Compute the ratio of the 
size of the image to the size of the object. Also the ratio of 
the image distance to the object distance. Each ratio to be 
expressed to the second decimal place. 

Size of image ( ab ) .... 

Size of object (AB) .... 

Distance of image to mirror .... 

Distance of object to mirror .... 

Ratio of sizes .... 

Ratio of distances .... 


65 












Experiment 33 — CONCAVE CYLINDRICAL MIRROR 

Place the mirror in a vertical position near the center of 
the right-hand page of your notebook. With a sharp pencil 
draw a line along the base of the concave surface. 

Remove the mirror and draw the chord connecting the two 
ends of the curve. At the mid-point of the chord draw a per¬ 
pendicular or principal axis. Chord and axis to be in dotted 
lines. 

Obtain the focal length and radius of curvature from the 
previous experiment and indicate on your drawing the lo¬ 
cation of the vertex (V), the principal focus (F), and the 
center of curvature (C). 

At a point midway between V and F draw a perpendicular 
AB, extending one centimeter each side of the axis. Place a 
pin at A and replace the mirror. Sighting along the edge of 
a ruler, draw two lines that if extended would appear to pass 
through the image of A. The sight lines are more easily 
drawn if, after the image is found, the eye is held stationary 
and the ruler then moved to the correct position. 

Remove the mirror and pin and extend the sight lines to 
the mirror and to the point of intersection. Lines back of the 
mirror are to be dotted. Connect A with the points where 
the sight lines strike the mirror. Show by arrows the direc¬ 
tion of the rays of light as they leave A and after reflection. 

Assuming the image of B to be similarly placed in respect to 
the axis, draw the line ab as the image of the object AB. 
Record in the tabulation the position, size, form and kind of 
the image. 

Place the mirror in the center of another page and make a 
second diagram with the object (AB) placed midway be¬ 
tween F and C. Describe the image. If an image or object 
is in front of the mirror, its location is given in relation to the 
points V, F and C. 


66 


Tabulation 


Location of Object 
Location of image 
Size of image 
Form of image 
Kind of image 


Between V and F 


Between F and C 


Optional 

In the second diagram measure the length of the image and 
its distance from the mirror. Compute the ratio of the size 
of the image to the size of the object. Also the ratio of the 
image distance to the object distance. Each ratio to be ex¬ 
pressed to the second decimal place. 

Size of image ( ab ) .... 

Size of object (AB) .... 

Distance of image from mirror .... 

Distance of object from mirror - 

Ratio of sizes .... 

Ratio of distances .... 


67 










Experiment 34 —SPHERICAL MIRRORS 


Part I — Focal Length 

Clamp the flame and concave mirror on the optical bench 
80 centimeters apart. Support the screen between the 
flame and mirror a little to one side of the line connecting 
their centers. Move the screen back and forth until a dis¬ 
tinct image is obtained. 

Measure and record as (A) the distance between the flame 
(object) and the center of the mirror. Record as (B) the dis¬ 
tance between the screen (image) and the mirror. Compute 
the focal length F from the mirror formula. 

Part II — Images 

From the results of Part I, calculate the radius of curvature 
of the mirror, which is twice the focal length. Place the flame 
at this distance from the mirror. It will then be at the 
center of curvature C. Obtain the image of the flame by 
holding the screen near the side of the flame. Move the 
screen until the image is very sharp or distinct. 

It is customary to call the flame the object. Is the image 
as now seen larger or smaller than the object? Is it erect or 
inverted? Where is it with reference to the center of curva¬ 
ture C, principal focus F, and vertex V? Is it real or virtual? 
Record the answers to those questions in the table below un¬ 
der the headings of “Size/’ “Form,” “Location,” and 
“Kind,” respectively. 

Place the object at the different locations indicated in the 
tabulation. Find the image in each case and describe it as 
above. 

Change the mirror about and use the convex surface. 
Place the flame near the mirror and describe the image. 
Repeat with the flame a meter from the mirror. 


68 



Tabulation 
Part I 

Distance from object to mirror (A) .... 

Distance from image to mirror ( B ) .... 

Focal length of concave mirror (F) .... 

Part II 

Description of Image Location Size Form Kind 

Object at C, concave mirror .... .... . 

Object beyond C .... .... . 

Object between C and F .... .... .... .... 

Object between F and V .... .... . 

Object near convex mirror .... .... .... .... 

Object a meter from mirror .... .... . 


Optional 

An object is placed 15 centimeters from a concave mirror 
whose radius of curvature is 12 centimeters. How far from 
the mirror is the image? Solve by formula and by con¬ 
struction. 


69 





















Experiment 35 — INDEX OF REFRACTION OF WATER 


Fill a six-inch battery jar with water until the surface is 
about one inch from the top of the jar. 

Place nails in the two holes of the index of refraction board. 
The head of the nails should be on the back of the board or 
on the side opposite the groove. 

Place a smaller block across the top of the jar and clamp 
it to the back of the refraction board in such a manner that 
the board will be in a vertical position with the upper edge 
of its groove just at the surface of the water at all points. 

Place a third nail on the upper edge of the board parallel 
with the other two nails. Looking down into the water, 
carefully place the nail on the edge in such a position that the 
three nail points will apparently be in the same straight line. 
Measure the distance from the center of the nail on the edge 
to the corner of the board. 

Remove the board from the water and take out the nails. 
Wipe the board and nails thoroughly dry. Draw a line MN 
across the center of the page of your notebook to represent 
the surface of the water. Place the board on the page with 
the upper edge of the groove on the line MN. Locate on the 
page the position of the nail in the air (A). By placing the 
point of the nail in the hole, mark the position of the nail 
near the surface of the water (S) and in the water (IF). 

Remove the board and draw the incident ray from IF 
through A to the point of incidence in the surface line MN. 
Connect the point of incidence to A as the refracted ray. 
Construct a normal to MN at the point of incidence. From 
a point on each of the rays equidistant from the point of 
incidence, construct a perpendicular to the normal. Measure 
the two perpendiculars and record as IN and RN. 

Compute the sine of the angle of incidence and the sine of 
the angle of refraction. Compute the index of refraction of 
light passing from water into air by the ratio of the perpen¬ 
diculars and by the ratio of the sines. 


70 



Tabulation 

Length of perpendicular (IN) 
Length of perpendicular (RN) 
Index of refraction (IN 4- RN) 
Hypotenuse of right triangles 
Sine of angle of incidence 
Sine of angle of refraction 
Index of refraction (Ratio of Sines) 


Optional 

By means of a protractor measure the angle of incidence 
and the angle of refraction. From the Table of Sines given 
in the Appendix obtain the sine of each angle and compute 
the index of refraction of light passing from water into air. 

Angle of incidence (degrees) 

Angle of refraction (degrees) .... 

Sine of angle of incidence .... 

Sine of angle of refraction .... 

Index of refraction .... 


71 









Experiment 36 — SPEED OF LIGHT IN GLASS 


Draw a line across the center of the right-hand page of 
your notebook. On this line place a point A, 3 centimeters 
from the end, and a point B, 10 centimeters from A. At the 
points A and B draw the lines AC and BD respectively, 
making angles of 45 degrees with the line AB. 

Place the block of glass in the position shown by dotted 
lines in the diagram. The ground edge of the block should 
be on the line AB. Place two pins in line AC about 3 cen¬ 
timeters apart, and looking through the glass from edge to 
edge, place a third pin at such a point E, on the lower edge 
of the block, that all three pins will appear to be in the same 
straight line. Slide the block along on the line AB and in 
a like manner determine the point F. 

Remove the glass and draw the lines A E and BF . Draw 
AG perpendicular to BD and BH perpendicular to AE. 
Erect a perpendicular (normal) to the line AB at the point B. 
Extend the lines BD and BF to a distance of 10 centimeters 
from B and at the extremity of each draw a perpendicular 
to the normal. Measure and record the various lines in¬ 
dicated in the tabulation. 

What do the lines AG and BH represent? What do the 
lines BG and AH represent? What does the ratio of MN to 
IF measure? What is proved by the comparison of the two 
ratios in the tabulation? 


72 



Tabulation 


Length of line BG .... 

Length of line AH .... 

Ratio of BG to AH .... 

Length of perpendicular MN .... 

Length of perpendicular XY .... 

Ratio of MN to XY .... 

Speed of light in air 300,000,000 m./sec. 

Speed of light in glass .... 


Optional 

Prove geometrically from your drawing that the two ratios 
in the tabulation are equal. 


73 













Experiment 37 — REFRACTION BY PRISMS 


Draw a line MN across a page of your notebook. Place 
the prism on end so that one side of its base will lie along the 
central portion of the line MN. With a sharp pencil trace 
the perimeter of the base of the prism. Place the prism 
on the other side of the line as in the diagram and again 
draw the perimeter. 

At a point B near the center of the side of the base of the 
prism, draw a line which will make an angle of 42 degrees 
with the base. Extend this line to the line MN at the point 
A. Connect A with a point C and make an angle of 42 
degrees with the other base. 

Place two pins on the line AB and replace the prism on the 
upper perimeter. Look through the prism from the opposite 
side, and by means of a ruler draw a line that if extended 
would appear to pass through the two pins or along the line 
AB. In a similar manner draw a line that coincides with the 
images of two pins in the line AC. 

Remove the prism and extend the lines just drawn to the 
perimeter in one direction and until they intersect in the 
other direction. Draw the path of the light as it passes 
through the prism. Draw a normal where it enters the glass 
and also where it leaves the glass. Measure the angles in¬ 
dicated in the tabulation. Letter all angles on drawing and 
in the tabulation. 

I. What do the lines AB and AC represent? 

II. What do the lines constructed on the opposite side of 
the prism represent? 

III. What does the intersection of the lines in II repre¬ 
sent? 

IV. In what direction is the ray of light bent as it enters 
and as it leaves? 


74 


Tabulation 


Angle of incidence ( ) 

Angle of refraction of prism ( ) 


. degrees 


degrees 


Sum of angles (incid. and refract.) 
Angle of deviation ( ) 


Refracting angle of prism ( ) 

Sum of angles (deviat. and prism) 


. degrees 
. degrees 
. degrees 
. degrees 


Optional 


Obtain from a Table of Sines given in the Appendix of 
Manual, the sine of one-half of the sum of the angle of 
deviation and the refracting angle of prism. Also the sine 
of one-half of the refracting angle of prism. Divide the first 
sine by the second and state what the quotient represents. 


75 





Experiment 38 — LENSES — FOCAL LENGTH AND 
IMAGES 


Part I — Focal Length 

Place a right-angled support on one end of the optical bench 
and in it clamp the gas burner so that the plane of the flame 
will be at right angles to the bench. Support the metal 
screen near the other end of the bench. Between the screen 
and flame support a lens holder containing the double convex 
lens of two-inch diameter. The centers of the flame, lens, 
and screen should be at the same height. Turn up the flame 
until it is quite high. 

Find by trial a position for the lens between screen and 
flame that will give a distinct image of the flame on the 
screen. Great care should be taken in moving the lens lest 
it fall from its holder and strike the bench. If the screw of 
the right-angled support is well loosened, the support will 
slide freely on the bench. Measure the distance from the 
lens to the flame and record as the object distance (A). 
Record the distance from lens to the screen as the image dis¬ 
tance (B). Substitute in the lens formula and compute the 
focal length. 


Part II — Images 

Place the gas flame and screen on opposite sides of the lens 
and each twice the focal distance from the lens. The flame 
and screen are now at points called secondary foci. De¬ 
scribe the image as to size, form, location, and kind. For 
Part II, turn off the gas until the flame is low. 

Place the flame between the principal focus (P.F.) and 
secondary focus (S.F.) of the lens. Move the screen until a 
sharp focus or image is obtained. Describe the image. 

Place the flame beyond the secondary focus or more than 
twice the focal distance from the lens. Find the image and 
describe it as above. 

Place the flame between the principal focus and lens. Can 
an image be obtained on the screen? Look through the lens 
at the flame and describe the image seen, 


76 


Replace the double convex lens by the double concave lens 
and describe the image obtained when the flame (object) is 
near the lens and also when the flame is at some distance 
(60 cm.) from the lens. 



Tabulation 
Part I 

Distance from object to lens (A) .... 

Distance from image to lens ( B ) .... 

Focal length of convex lens (F) .... 

Part II 

Description of Image Location Size Form Kind 

Object at S.F. convex lens .... . 

Object between P.F. and S.F. .... . 

Object beyond S.F. .... . 

Object between P.F. and lens .... . 

Object near concave lens .... ... . 

Object 60 cm. from lens .... . 


Optional 

A three-inch slide is to be projected on a screen 20 feet 
away from the lantern, so that the picture will be 8 feet 
long. Find the focal length of the lens required. 


77 



















Experiment 39 — COEFFICIENT OF 
LINEAR EXPANSION 


Fill the boiler about one-half full of water and light the 
gas. Regulate the gas so that the flame does not come up the 
side of the boiler. 

Measure to the nearest millimeter the length of the metal 
rod which is held in the center of the steam jacket. 

Before replacing the jacket on the stand determine the 
method of reading the micrometer screw. (Determine how 
far the screw moves lengthwise when it is turned through 
one division on the disc or circular scale.) 

Replace the jacket on the stand ^iid turn the micrometer 
screw until it just touches the end of the metal rod. This 
point of contact can be accurately determined within one di¬ 
vision of the circular scale by the sense of touch, if the end 
of the rod is moved slightly up and down as the screw is 
moved slowly toward the rod. 

Read the linear and circular scales. If the linear scale is 
not numbered, consider the line nearest the end of the jacket 
as the zero line. 

Turn the screw back three or four millimeters to allow for 
expansion. Connect the jacket to the boiler and pass steam 
through for five or six minutes. 

Determine the temperature of the room which may be con¬ 
sidered as the temperature of the rod before expansion. The 
final temperature of the rod will be that of the steam, 100 
degrees C. 

While the steam is still passing, take the second microm¬ 
eter reading as before. Place a cloth between the hand and 
the jacket, as it is too hot to touch. 

From the original length, change in temperature, and ex¬ 
pansion, compute the coefficient of linear expansion of the 
rod. 


78 



Tabulation 


Length of rod 

.... mm. 

Micrometer reading 

.... mm. 

First temperature 

-deg. C. 

Second temperature 

-deg. C. 

Micrometer reading 

.... mm. 

Expansion of rod 

.... mm. 

Coefficient of expansion 



Optional 

The steel rail of a railroad track is 33 feet long. If the cold¬ 
est temperature is 30 degrees below zero, F., and the warmest 
120 above, what space should be left between rails if laid 
when the temperature is 72 degrees, F.? 


79 












Experiment 40 — SPECIFIC HEAT OF METALS 


Fill the boiler about two-thirds full of water and place on 
the tripod. Regulate the gas so that none of the flame comes 
up the side of the vessel. (A 600-cc. glass beaker may be 
used for the boiler.) 

Place a thread through the ball and make a loop of such 
length that, when suspended from a small stick placed across 
the top of the boiler, the ball will be entirely immersed in the 
water. Weigh the ball and thread to the nearest tenth of a 
gram and suspend it in the boiling water. 

Weigh the dry calorimeter. Fill the calorimeter about 
three-fourths full of water at a temperature a little (3 or 4 
degrees) below that of the room. Weigh the calorimeter 
and contents. 

Take the temperature of the water, estimating tenths of a 
degree, and immediately transfer the ball to the calorimeter. 
Be careful to transfer as quickly and with as little water as 
possible. By means of the thread move the ball up and 
down in the water and watch the thermometer. 

Record the highest temperature that can be obtained. 
This is the resulting or final temperature of the ball and 
water. 

The temperature of the boiling water and first temperature 
of the ball may be taken as 100 degrees Centigrade. 

Compute the number of calories given off by the ball and 
the number absorbed by the water. By the method of mix¬ 
tures compute the specific heat of the ball. 


80 



Tabulation 

Material tested 
Weight of the ball 

Weight of the calorimeter .... 

Weight of the calorimeter and water .... 

Weight of the water taken .... 

Temp, of boiling water or ball _ 

Temp, of calorimeter and water .... 

Resulting temperature .... 

Fall of temperature of ball .... 

Rise of temperature of water .... 

Specific heat obtained .... 

Correct specific heat .... 

Optional 

The vessel will change temperature the same as the water 
it contains. If the specific heat of the vessel is 0.1, compute 
the heat absorbed by the vessel. Taking this into consider¬ 
ation, compute again for a more accurate specific heat of the 

ball. 


81 














Experiment 41 — TEMPERATURE OF GAS FLAME 


Cut from the spool of chromel wire No. 28 a piece about 
a foot long. Fasten one end to an iron ball by putting it 
through the hole and then twisting the end several times 
around the wire above the ball. In the other end of the wire 
twist a loop large enough to go over the head of a spike. The 
ball should hang about eight inches below the nail. 

Weigh the ball and wire on a platform balance to the near¬ 
est tenth of a gram. Place the nail in a clamp on the vertical 
support rod and suspend the ball so that it will be entirely 
surrounded by the upper part of a Bunsen burner flame. 

Weigh the calorimeter. Fill it about three-fourths full of 
cold water and weigh again. The temperature of the cold 
water should be about five or six degrees below room tem¬ 
perature. 

When the ball has been in the flame three or four minutes 
after becoming red-hot, take the temperature of the cold 
water. Move the flame to one side and quickly submerge 
the ball in the water by bringing the vessel up from under¬ 
neath the ball. 

Put in a thermometer and- keep the water in motion by 
stirring with the thermometer and by raising and lowering 
the vessel. Record the highest temperature obtained. 

Compute the heat received by the water and by the vessel. 
(Consider the specific heat of the vessel to be 0.1). With x 
as the change of temperature of the ball, express the number 
of calories given off by the ball. Equate the calories given 
off and the calories received and compute the fall of tem¬ 
perature of the ball. Determine the temperature of the flame. 


82 



Tabulation 

Weight of calorimeter .... 

Weight of calorimeter and water .... 

Weight of water .... 

Temperature of cold water .... 

Resulting temperature .... 

Calories received by water .... 

Calories received by vessel .... 

Calories given off by ball .... 

Fall of temperature of ball .... 

Temperature of flame (Centigrade) .... 

Optional 

A 2-pound iron ball is heated for some time in a furnace 
and then dropped into 6.8 pounds of water at 40 degrees F. 
The resulting temperature of the water is 100 degrees. 

Compute the temperature of the furnace on the Fahrenheit 
scale. 


83 










Experiment 42 — LATENT HEAT OF SNOW 


Weigh the dry calorimeter to the nearest tenth of a gram. 

Fill the calorimeter about one-half full of water ten or 
twelve degrees Centigrade above room temperature and 
weigh again. 

After weighing and immediately before adding snow, de¬ 
termine the temperature of the water estimating to the tenth 
of a degree. 

Add dry snow slowly until the temperature of the water 
after the snow is melted is as far below room temperature as 
the beginning temperature was above room temperature. 
When sure that all the snow is melted, read and record the 
coldest temperature obtained. 

Weigh the calorimeter and contents and compute the 
weight of snow melted. 

Compute the number of calories given off by the hot 
water and by the calorimeter. (Specific heat of calorimeter, 
0 . 1 .) 

Compute the number of calories received by the cold 
water formed from the melted snow. With x as the latent 
heat of snow, express the number of calories received by the 
snow when melting. 

From the equation, heat given off is equal to the heat 
received, compute the latent heat of snow, or the number of 
calories required to melt one gram of snow. 


84 


Tabulation 


Weight of calorimeter .... 

Weight of calorimeter and water .... 

Weight of water .... 

Temperature of warm water .... 

Weight of calorimeter, water, and snow .... 

Weight of snow .... 

Temperature of mixture .... 

Calories given off by hot water .... 

Calories given off by vessel .... 

Calories received by cold water .... 

Calories received by melting snow .... 

Computed latent heat of snow .... 

Correct latent heat of snow .... 

Optional 

If 10 pounds of ice at 32 degrees F. are placed in 11 pounds 
of water at 182 degrees F., the resulting temperature will be 
42 degrees. Compute the latent heat of ice in British 
thermal units. 


y 


85 






Experiment 43 — LATENT HEAT OF STEAM 


Place the boiler one-half filled on the tripod and screw the 
top on steam-tight. Connect the delivery or glass tube to 
the outlet of the boiler with a rubber tube. 

Weigh the dry calorimeter to the nearest tenth of a gram. 

Fill the calorimeter about three-fourths full of the coldest 
water obtainable from the tap which should be about ten 
degrees below room temperature. Weigh the calorimeter 
and water to the nearest tenth of a gram. 

When a strong jet is issuing from the delivery tube of the 
boiler, note accurately the temperature of the water in the 
calorimeter and immediately wipe the end of the delivery 
tube dry and plunge it nearly to the bottom of the water in 
the calorimeter. 

Place the thermometer in the calorimeter using it and the 
delivery tube as stirring rods. When the temperature of the 
water is about as many degrees above room temperature as 
the cold water was below, remove the delivery tube with as 
little water as possible. Now watch the thermometer and 
record the highest temperature obtained. 

Weigh the calorimeter and contents. The increase in 
weight will give the weight of the steam condensed. The 
temperature of the steam may be taken as 100 degrees Centi¬ 
grade. 

Compute the latent heat of steam, or the number of 
calories liberated as one gram of steam condensed. The heat 
received by the calorimeter (Sp. heat, 0.1) should be consid¬ 
ered in the computation. 


86 



Tabulation 

Weight of calorimeter 

Weight of calorimeter and water 

Weight of cold water 

Weight of calorimeter, water, and steam 

Weight of condensed steam 

Temperature of steam 

Temperature of cold water 

Temperature of mixture 

Rise of temperature, cold water 

Fall of temperature, condensed steam 

Latent heat of steam 

Correct latent heat of steam 


Optional 

Two pounds of steam at 212 degrees F. condensed in 
50 pounds of water at 40 degrees F. will raise the temperature 
of the water to 84 degrees F. Compute the latent heat of 
steam in British thermal units. 


87 










Experiment 44 — EFFICIENCY OF GAS HEATING 


Clamp the Thorp gauge or gas meter in a vertical position. 
Connect the upper end of the gauge to a Bunsen burner and 
the lower end to a gas-cock. Observe that the instrument 
indicates the number of cubic feet passing through per hour. 

Weigh the glass vessel on the platform balance to the near¬ 
est gram. Fill the vessel about two-thirds full with water at 
about six degrees below room temperature and weigh again. 

Light the burner and regulate the flow of gas to six cubic 
feet per hour. Determine the exact temperature, estimating 
to the tenth of a degree, of the cold water and immediately 
place the burner under the vessel. 

After the water has been heating for exactly two minutes, 
remove the flame from underneath the vessel and determine 
the temperature of the water. 

The fuel value of gas may be considered as 140,000 cal¬ 
ories per cubic foot. Determine the amount of gas used dur¬ 
ing the two minutes and compute the number of calories 
equivalent or the input. 

From the change of temperature, weight of vessel and 
weight of water used, compute the calories received by vessel 
and water or the output. (The specific heat of the vessel is 
0.2.) Compute the efficiency of the gas burner. 


88 



Tabulation 

Weight of glass vessel 
Weight of vessel and water 
Weight of water 
Temperature of cold water 
Resulting temperature 
Calories received by water 
Calories received by vessel 
Output in calories 
Reading of gauge 
Time of heating 
Cubic feet of gas burned 
Input in calories 
Efficiency of gas burner 


Optional 

With gas at 75 cents per 1000 cubic feet, find the cost of 
producing 1,000,000 calories of heat with a Bunsen burner. 


89 











Experiment 45 — MAGNETIC FIELDS 


Lay the magnet in the groove in the center of the magnet 
board and cover with a large sheet of paper. With the sieve 
box sprinkle iron filings evenly on the paper from a height of 
about a foot. A more even distribution of the filings will be 
obtained if the box is moved back and forth horizontally than 
if given a vertical shake. It is best not to use too many fil¬ 
ings and to tap the board gently with the rubber stopper. 
Have the result accepted by the instructor. 


First Method of Record 

Draw in your notebook a diagram or picture of the magnet 
and iron filings as obtained on the paper. Draw the magnets 
about one-third size and represent the filings by short dashes. 

Replace the filings in the box and repeat the process plac¬ 
ing magnets in the two grooves with their unlike poles op¬ 
posite. 

For a third diagram place the like poles opposite. 

Second Method of Record 

Replace the filings in the sieve box and cover the magnet 
with a sheet of blueprint paper, colored side up. The paper 
should be held in place and kept from curling by using thumb 
tacks at the corners or rulers on the edges. Sprinkle on filings 
as before. Place the apparatus in the direct sunlight and 
leave untouched for a period of from 45 to 60 seconds or until 
the uncovered portion of the paper has changed color con¬ 
siderably. Another test is to moisten the finger and touch 
the edge of the paper. If the paper turns to a decided blue, 
it is sufficiently exposed. 

Pour off the filings and wash the paper in the water tank. 
When first placed in the water, the paper should be kept in 
motion for a few seconds. The washing should continue for 
six or seven minutes or until strong blue and white effects 
are obtained. When thoroughly washed, pin it up to dry. 


90 


Repeat the process placing magnets in the two grooves 
with their unlike poles opposite. 

Repeat with like poles opposite. 

When the prints are thoroughly dried, they are to be 
trimmed and inserted in the notebook. 



1. For convenience of reference what name is given to the 
curves along which the filings have arranged themselves? 

2. Each little filing as it falls near the large magnet be¬ 
comes a small magnet and its position is determined by the 
resultant of the forces of attraction and repulsion. What 
definition may be given for the lines named in question 1? 

3. Describe the direction of these lines in each of the three 
diagrams or prints. 


Optional 

Make a fourth trial and diagram using two magnets with 
unlike poles opposite. Place an iron washer on the board 
between the north and south poles of the two magnets. 
Why are there no lines of force above the washer? 


91 



Experiment 46 — ELECTROMOTIVE FORCES 


Part I — Effect of Using Different Metals 

Fill the glass jar about two-thirds full of the sulphuric 
acid solution. Connect two short wires to the binding posts 
of the porcelain holder. Clamp in the holder strips of copper 
and zinc that have been thoroughly polished with sand 
paper. Connect the exposed ends of the two wires to the 
binding posts of the voltmeter. The positive electrode of the 
cell must be connected to the positive binding post (right- 
hand side if not marked) of the voltmeter. When the volt¬ 
meter is reading correctly the polarity of the electrodes used 
in the cell may be determined by the connections. 

Read and record the voltage. Repeat the test using a 
carbon strip in place of the copper. Continue the testing 
until all possible pairs of the five elements have been tried. 
Record the materials, polarity, and voltage in the manner 
suggested by the tabulation below. 


Part II — Effect of Using Different Electrolytes 

Determine the voltage when zinc and copper electrodes 
are immersed in the following electrolytes: 

(a) dilute sulphuric acid 

( b ) dilute hydrochloric acid 

(c) solution of common salt 

( d ) solution of sal ammoniac 

(e) solution of sugar 

(/) water from tap 

The plates should be very thoroughly rinsed and wiped each 
time before placing them in a new liquid. Great care must 
be taken to see that each solution is returned to the proper 
bottle or jar. 


92 


Tabulation 

Electrolyte Pos. Electrode Neg. Electrode Voltage 


From the results obtained, arrange the five elements in a 
column in such an order that each element will be negative in 
respect to all elements above it and positive to all elements 
below it. Such a column is called an electromotive series. 

Optional 

Effect of Size of Cell 

Connect the simple cell (copper and zinc in sulphuric acid) 
to the voltmeter and record the voltage. Care should be 
taken to connect positive electrode (copper) to the positive 
(right-hand side if not marked) binding post of the meter. 
Move the plates as far apart as possible in the jar and record 
reading. Lift the plates one-half out of the liquid and record. 

What conclusion can be stated concerning the relation 
between the size of the cell and the electromotive force? 


93 


Experiment 47 — RESISTANCE: AMMETER- 
VOLTMETER 


Part I — Ohm’s Law 

Ohm’s law states a relation between the voltage, amperage, 
and resistance. If the amperage of the current flowing 
through a resistance and the voltage causing it to flow are 
measured, the resistance can be computed by applying the 
law. 

Connect the wire, the resistance of which is to be measured, 
a battery, a key, and an ammeter in series as shown in the 
diagram. For a battery use a small storage cell or two dry 
cells connected in series. Note that the meter may be used 
as an ammeter or a voltmeter depending on the binding posts 
used for the connections. 

Close the key and record the reading of the ammeter, es¬ 
timating tenths of a division. When using dry cells, take 
the reading when the pointer first comes to rest and imme¬ 
diately open the key. 

Disconnect the ammeter from the circuit and connect the 
key to the end of the wire. Connect the voltmeter as a 
shunt across the terminals of the wire. Record the reading 
of the voltmeter when the key is closed. 


Part II — Specific Resistance 

The resistance of a wire may be computed by multiplying 
the resistance of a mil foot of the wire by the length in feet 
and dividing by the square of its diameter in mils. 

Measure the length in feet of the wire used in Part I. Use 
a micrometer screw and determine the diameter of the wire. 
If the screw reads in millimeters, change to inches and to 
mils. 

Substitute this length and diameter and the resistance 
obtained in Part I in the above formula and solve for the 
resistance of a mil foot or the specific resistance of the alloy 
used in the wire. 


94 




Tabulation 

Amperage through the wire 
Voltage across terminals of wire 
Resistance, computed (Ohm’s law) 
Length of wire (feet) 

Zero reading of micrometer 
Diameter of wire (millimeters) 
Diameter of wire (inches) 
Diameter of wire (mils) 

Specific resistance 


Optional 

Compute the resistance of an aerial that has 100 feet of 
No. 14 aluminum wire. For necessary data see tables in 
Appendix. 


95 


























Experiment 48 — RESISTANCE: WHEATSTONE BRIDGE 


The Wheatstone bridge consists of a divided circuit; each 
division contains two resistances. The current divides at 
A, a part flowing through R and X and a part through m 
and n. If a galvanometer is connected to C and to such a 
point D on the wire mn that no current flows through the 
galvanometer, then C and D are of the same pressure and 
by applying Ohm’s law it can be shown that: 

Resistance (X) : Resistance (R) :: Length (n) : Length (m). 

Connect the apparatus as shown in the diagram. For the 
unknown resistance use a piece of German-silver wire No. 30 
about four feet in length. After the wire is connected, de¬ 
termine the exact length of wire between the binding posts. 

A Wheatstone bridge to be used correctly must have the 
point D somewhat near the middle of the wire mn, or a re¬ 
sistance near that of X must be placed in the resistance 
box R. 

To determine the proper resistance for R, place in 10 ohms 
and note the direction of deflection of the galvanometer. 
(Care must be taken to close the battery circuit key first and 
then close, for a moment only, the galvanometer circuit key 
at the point D.) 

Place 100 ohms in R. If the deflection is in the same direc¬ 
tion, the proper resistance is below 10 ohms; but if the direc¬ 
tion of deflection changed then more resistance is needed in 
R. Start again with 10 ohms in R and change by one ohm 
at a time until the direction of deflection changes. The last 
resistance tried is sufficiently near X to be considered the 
proper resistance for R. 

See that all points of contact, binding posts and plugs, are 
tight and make final adjustment by moving the contact 
point D back and forth on the wire until a point is found 
where closing both keys no deflection is obtained. 

Record the resistance R and the lengths of the portions of 
the wire m and n. Substitute in the bridge formula and solve 
for the unknown resistance X. 

Determine by means of a micrometer screw, the diameter 
of the wire X in millimeters. Change to inches and record 

96 


in mils. Substitute the length of the wire in feet, the resist¬ 
ance found in ohms, and the diameter in mils in the resist¬ 
ance formula and solve for the specific resistance of German 
silver. 



Tabulation 

Length of German-silver wire .... ft. 

Resistance in box R 
Length of wire (m) 

Length of wire (n) 

Resistance of wire (X) 

Diameter of German-silver wire 
Diameter of German-silver wire 
Diameter of German-silver wire 
Specific resistance of German silver 

Optional 

Apply Ohm's law to the four parts of the circuit: A to C, 
C to B, A to D, D to B, and prove the bridge formula 
(X : R :: n: m). 

Note: If C and D are of the same pressure then the voltage 
between A and C must be equal to the voltage between A and D 
and likewise between C and B and between D and B. 


. mm. 

. mm. 

. ohms 
. mm. 

. in. 

. mils 
. ohms 


97 























Experiment 49 — SERIES CIRCUIT 


Part I — Amperage 


Connect the ammeter, the two rows of resistance coils of a 
resistance box, a key, and a battery all in series as shown in 
the diagram. For the battery use two dry cells connected 
in series. 

Remove the three-ohm plug from one row of resistances 
and a one-ohm plug from the other row. The other plugs 
should be firmly placed which can be done by giving them a 
partial turn under slight pressure. (Loosen all plugs when 
through with the experiment.) 

Close the key and take as the ammeter reading the point 
where the pointer first comes to rest. When using dry cells, 
never keep the key closed any longer than is absolutely 
necessary to secure the reading. 

For convenience we speak of the current as coming from 
the positive terminal of the battery. Connect the ammeter 
between the key and the negative terminal of the battery 
and again determine the amperage of the circuit. 





Part II —Voltage 


Disconnect the ammeter from the circuit. Use the volt¬ 
meter binding posts of the meter and connect as a shunt 
across the terminals (A and B) of the one-ohm resistance. 
Close the key and read the voltmeter. 

Connect the voltmeter across the terminals (C and D) of 
the three-ohm resistance and determine the voltage. Now 
connect the voltmeter as a shunt to both resistances in series 
(between A and D). 


98 























Part III — Resistance 


From the amperage of the circuit and the voltage between 
A and D, apply Ohm’s law and compute the resistance of the 
circuit from A to D. Apply Ohm’s law to the partial circuits 
A to B and C to D and compute the resistance in each. 



Tabulation 

Amperage at pos. terminal - 

Amperage at neg. terminal - 

Voltage between A and B .... 

Voltage between C and D .... 

Voltage between A and D .... 

Resistance between A and B ( x ) 1 ohm 

Resistance between C and D ( y ) 3 ohms 

Resistance between A and D (x + y) 4 ohms 

Resistance (x) by Ohm’s law .... 

Resistance (y) by Ohm’s law .... 

Resistance (x + y ) by Ohm’s law .... 

State conclusions that can be drawn concerning amperage, 
voltage, and resistance of a series circuit. 

What relation is shown between the voltage drop and the 
resistance along a series circuit? 

Optional 

Make a neat diagram (use ruler) of the circuit showing all 
connections of ammeter and voltmeter made in the experi¬ 
ment. 


99 








Experiment 50 — PARALLEL CIRCUITS 


Part I — Amperage 

The two rows of resistance coils in the resistance box are 
to be used as two separate resistance boxes (x and y). Con¬ 
nect a battery of two dry cells in series, the ammeter, a key, 
and the resistances in a circuit as shown in the diagram. 
Note that the current divides: a part goes through the re¬ 
sistance x and a part through the resistance y. 

Place one ohm in the x division and three ohms in the y 
division. Read and record the reading of the ammeter. 
This will be the amperage in the main circuit. 

Disconnect the ammeter from the main circuit and con¬ 
nect it between the key and the resistance x. This reading 
or amperage will be the part passing through the one ohm. 
In a like manner connect the ammeter so as to determine the 
amperage of the current flowing through the three ohms. 

Part II — Voltage 

. Connect the battery, key, and resistance boxes as in Part I. 
Use the meter now as a voltmeter and connect to the ter¬ 
minals of x. Close the key and determine the voltage or pres¬ 
sure causing the current to flow through the one ohm. 

Connect the voltmeter so as to determine the voltage caus¬ 
ing current to flow through the three ohms. 

Part III — Resistance 

Compute the joint resistance of x and y, or a single resist¬ 
ance that would have the same effect in the circuit, by apply¬ 
ing Ohm’s law. (Divide the voltage across the parallel cir¬ 
cuit by the sum of the currents in the two branches.) 

The resulting resistance of two parallel circuits can be ob¬ 
tained by the formula: R equals the product of the individual 
resistances divided by their sum. 


100 


r 


[ii 



I_ 


I_ 



Tabulation 

Amperage of main circuit .... 

Amperage of x branch .... 

Amperage of y branch .... 

Voltage across x branch .... 

Voltage across y branch .... 

Resistance in x circuit .... 

Resistance in y circuit .... 

Resistance of x and y (Ohm’s law). .... 

Resistance of x and y (Formula) .... 

State the relation between the resistances and the am¬ 
perages of a divided circuit. 

State a conclusion concerning the voltage causing the cur¬ 
rent to flow through to the different resistances in parallel. 

How could the magnitude of a single resistance that would 
take the place of two resistances in parallel be computed? 

Optional 

Make a neat diagram of the circuit showing all connections 
of ammeter and voltmeter made in the experiment. 


101 


































Experiment 51 — BATTERY CONNECTIONS 

Part I — Voltage 

Determine the voltage of each of three dry cells by con¬ 
necting them individually to the voltmeter binding posts of 
the meter. 

Connect two of the cells in series, that is, connect the zinc 
of one to the carbon of the other and the remaining zinc and 
carbon to the voltmeter. In a like manner find the voltage 
of the three cells when connected in series. 

Connect two of the cells in parallel, that is, zinc to zinc and 
carbon to carbon with a zinc connection to one post and a 
carbon connection to the other post of the voltmeter. In a 
like manner find the voltage of the three cells when connected 
in parallel. 

Part II — Amperage 

Connect two cells in series. Place in the external circuit 
an ammeter, key, and resistance box. Determine the am¬ 
perage with each of the following resistances in the circuit: 
10, 5, 0.2, 0.1 ohms. 

The key should be closed only while taking a reading of 
the meter. The position where the pointer first comes to 
rest should be taken as the reading. 

Change the connections of the two cells from series to 
parallel. Find the amperages obtained with the same indi¬ 
vidual resistances in the external circuit. 

What general conclusions can be drawn concerning the 
voltage of series and parallel batteries? When is it better to 
connect in series? In parallel? 


102 


Tabulation 
Part I — Voltage 

Arrangement of Cells Voltage 

Single cell, No. 1 .... 

“ “ No. 2 
“ “ No. 3 

Two cells in series .... 

Three cells in series .... 

Two cells in parallel .... 

Three cells in parallel .... 


Part II — Amperage 


Battery 

Two cells in series 

tt it a it 

u it it it 

tt tt tt tt 

Two cells in parallel 

u tt tt u 

tt tt a tt 

tt tt tt tt 


External Resistance Amperage 

10 ohms .... 

5 “ 

0.2 “ 

0.1 " 

10 

5 “ 

0.2 “ 

0.1 “ 


Optional 

Find the voltage of four cells connected in multiple series. 
Arrange the four cells in two rows, each consisting of two 
cells in series. The rows are connected in parallel. 


103 










Experiment 52 — TERMINAL VOLTAGE AND 
RESISTANCE OF CELL 

Part I — Terminal Voltage 

Connect the terminals of a dry cell to the binding posts 
of a voltmeter and record the reading. This is called the 
electromotive force (E) or open circuit voltage of the cell. 

Leave the voltmeter connected to the cell and connect 
also to the binding posts of the cell a second (external) cir¬ 
cuit containing a key and a resistance box. If the key is 
closed, the voltmeter will give, not the voltage of the cell, 
but the voltage used to force the current through the ex¬ 
ternal circuit. Record the reading when the key is closed as 
the terminal voltage (V). 

Place 100 ohms in the resistance box or external circuit. 
Close the key and record the terminal voltage. Repeat with 
0.1 ohm in the box. Give reasons for the results obtained. 

Part II — Resistance of Cell 

Use apparatus as connected in Part I, except that the bat¬ 
tery should be three dry cells connected in series. Determine 
the terminal voltage when each resistance given in the tabu¬ 
lation below is placed in the resistance box or external cir¬ 
cuit. Before each trial and while the key is open, read and 
record the electromotive force. 

If Ohm’s law is applied to the entire circuit 

. Electromotive force of battery (E) 

mperage - Ext> R es i s t. (R) + Int. Resist, (r) 

If the law is applied to the external circuit only 

Terminal voltage (V) 
mperage Externa i resistance (R) 


104 




As the amperage is the same through the circuit, equate 
the last members of the above equations and derive a for¬ 
mula for (r). Compute r in each of the trials. From the 
average determine the internal resistance of one dry cell. 




"1 


i 



Tabulation 

Part I — Terminal Voltage 

Electromotive for<^ of cell 
Terminal voltage (V) with 100 ohms 
Terminal voltage (V) with 0.1 ohms 


Part II — Resistance of Cell 

Ext. Resist. (R) E.M.F. (E) Ter. Volt. (V) Int. Resist, (r) 
1.7 ohms .... .... .... 

1.4 ohms .... .... .... 

1.0 ohms .... .... _ 

.7 ohms .... .... _ 

.4 ohms .... _ _ 

Average resistance of one dry cell .... 


Optional 

What is the line drop or voltage drop per mile in a trolley 
line carrying 150 amperes, if the line is No. 1 copper wire? 


105 


























Experiment 53 — ELECTROMAGNETISM 


Part I —Thumb Rule 

Connect an electrode of a dry cell to one binding post of 
the key by means of a copper wire about three feet long. 
Complete the circuit from key to battery with a short wire. 

Place some portion of the long wire parallel to and above 
the magnetic needle of a compass so that the current will 
flow from the south to the north. Record the deflection of 
the north pole (east or west) when the key is closed. 

Determine the deflection of the north pole when the cur¬ 
rent is going in the different directions and locations indi¬ 
cated in the table below. In the last four determinations the 
compass should be placed on the end of a block of wood and 
the wire held in a vertical position. 

Represent each of the last four trials with a diagram. 
Represent the cross-section of the wire by a small circle. If 
the current is coming up, place a dot in the circle; if going 
down, place a cross in the circle. Draw the needle near the 
circle showing its exact position in relation to the wire and 
the direction of the N pole when the current was passing. 

Tabulation 

Direction of Current Deflection of N Pole 

Going north above needle .... 

Going north below needle .... 

Going south above needle .... 

Going south below needle .... 

Going up near N pole .... 

Going up near S pole .... 

Going down near N pole .... 

Going down near S pole .... 

State a hand rule that expresses the relation between direc¬ 
tion of current and the deflection of the N pole. Apply the 
rule to the first four trials in the table. When grasping the 
wire, the fingers must be on the same side of the wire as 
the needle. 


106 





Part II — Electromagnets 


A B 

Form a close wound coil by wrapping the longer wire ten 
or twelve times around a soft iron nail. Place the coil in an 
east and west direction with one end near the side of the 
compass. Note the direction of the needle when the current 
is flowing. 

Draw a diagram of the coil and needle. Indicate the direc¬ 
tion of current by means of arrows and label the north pole. 
Notice which type of winding (A or B) is used in making the 
coil. 

Place the compass at the other end of the coil. Note the 
position of the needle when the key is closed. Represent this 
needle in the drawing. State the thumb rule for electromag¬ 
nets and apply it as a check to the drawing. 

Optional 

Connect the two binding posts of the key to the two outlets 
underneath the edge of the table or to some other assigned 
source of direct current. Place some part of the wire above 
the compass and note the deflection when the key is closed. 
By the rule stated above determine the polarity of the outlets 
or source. 


107 






Experiment 54 — ELECTRIC BELL 

Remove the iron cover from the bell. Beginning at one of 
the binding posts, trace the path of the current by way of the 
coils of wire and other connections to the other binding post. 

Draw a skeleton diagram (similar to the one here shown) 
of the parts of the bell. Represent a few turns of wire around 
the cores of the electromagnets in the proper direction. 
Represent the path of the current through other wire connec¬ 
tions by means of lines. Where the current passes through 
metal parts indicate its path by small arrows. 

Write a concise description or explanation of how the 
hammer of the bell is kept in vibration. 



Connect a bell, two keys, and a dry cell in such a way that 
closing either key will ring the bell. Show these connections 
in your notebook by a diagram. This will represent con¬ 
nections when front and rear buttons ring the same bell. 

Show by diagram the connections when each button rings 
a separate bell with but one battery. 

108 


















Experiment 55 — TELEGRAPHY 


1. Explain the action in the receiver when the circuit is 
closed by pressing the key down in the transmitter. 

2. Explain the action in the receiver when the circuit is 
opened by the transmitter. 

3. Explain how the dot and the dash are produced by the 
transmitting operator. 

4. Explain how the dot and the dash are recognized by 
the receiving operator. 

5. Explain the purpose of the switch on the transmitter. 

With the student on the opposite side of the table, set 
up a telegraph system of two stations. For the line wire use 
a long piece of insulated wire. Use support rods and clamps 
for telegraph poles. Connect to gas-cock for ground circuit. 

Place in your notebook a neat and labeled diagram of 
your apparatus and connections. 

Try communication with the Morse Code. 


A ._ 

H .... 

0_ 

V 

B _ 

I . . 

P _ 

W 

C _ 

J _ 

Q- 

X 

D _ 

K_ 

R 

Y 

E . 

L _ 

S ... 

Z 

F _ 

M_ 

T _ 


G_ 

N _. 

U _ 



Optional 

Use a relay and connect a local circuit of sounder and 
battery at one station. 


109 


Experiment 56 — ELECTROLYSIS 

Part I — Copper Plating 

By means of a voltmeter determine the positive terminal 
of the source of current that is to be used in the experiment. 
(A small motor-generator, storage cell, or three dry cells 
connected in series may be used as the source.) If the cur¬ 
rent is supplied through outlets on the table, the positive of 
the source may be indicated as east or west, right or left. 

Fill the tumbler or jar of a student demonstration battery 
half full of a solution of copper sulphate. Place in the holder 
a rod of carbon and a strip of copper. Connect the electrodes 
to the current source in such a manner that the current will 
pass from the copper to the carbon. 

Let the current pass for one minute and describe the ac¬ 
tion taking place on each electrode. 

Change the connections at the source so that the current 
will pass from the carbon to the copper. Describe the action 
taking place on each electrode. 

In each test what must have been the relation between the 
direction of the current and the direction of the movement of 
copper ion? 

Tabulation 

Position of positive of current source .... 

Current passes from copper to carbon 
Effect on carbon electrode .... 

Effect on copper electrode .... 

Current passes from carbon to copper 

Effect on carbon electrode .... 

Effect on copper electrode .... 

Direction of copper ion movement .... 


110 


Part II — Storage Cell 

Fill the battery jar half full of ten per cent solution of 
sulphuric acid. Place in the holder two well sandpapered 
strips of lead. Connect the lead electrodes to the voltmeter 
and determine if there is any voltage. 

Mark one of the lead plates P and the other plate N. Con¬ 
nect the plates to the source of current in such a manner that 
the current will enter at the positive plate. Let the current 
(charging current) flow for one minute. Examine the plates 
and describe the effect, if any, on each plate. 

Connect the charged cell to the voltmeter and determine 
the direction of the discharging current through the cell. 
Record the voltage of the storage cell. 

Leave the cell connected to the voltmeter until it is com¬ 
pletely discharged. Examine the plates and describe the 
changes, if any, on each plate. 


Tabulation 

Voltage of two lead plates in acid 
Direction of charging current in cell 
Change on P plate during charge 
Change on N plate during charge 
Direction of discharging current in cell 
Voltage of charged storage cell 
Change on P plate during discharge 
Change on N plate during discharge 


Optional 

Conductivity of Water 

Fill the tumbler or battery jar with tap water. Place 
two copper plates in the holder. Connect the cell and an 
ammeter in series with the source of current. Does any 
current flow? Sprinkle salt in the water and watch the 
ammeter. Explain. 


Ill 






Experiment 57 — EFFICIENCY OF ELECTRIC HEATING 

Weigh the metal vessel on a platform balance to the near¬ 
est tenth of a gram. Weigh the vessel one-half full of water 
four or five degrees below room temperature. 

Determine the amperage of a 60-watt lamp by connecting 
it in series with an A.C. ammeter of one-ampere range. To 
measure the voltage connect the voltmeter to the terminals 
of the lamp socket. If the proper meters are not available, 
satisfactory results may be obtained by using the wattage 
given on the lamp. 

By means of a large universal clamp support an electric- 
light socket in a vertical position so that the lamp can be 
raised or lowered on the support rod. 

Take the exact temperature of the water and lower the 
lamp into the vessel until the brass base is just above the 
surface of the water. Connect the lamp to the A.C. outlet 
on the table and pass current through the lamp for exactly 
three minutes. Record the resulting temperature. 

Compute the number of calories received by the water 
and by the vessel. (Specific heat of the vessel is 0.1.) 
Record the total number of calories received as the output. 

From the wattage and time compute the number of watt- 
seconds or joules. From the heat equivalent of an electric 
current compute the input or the number of calories gener¬ 
ated by the number of watt-seconds used. Compute the 
efficiency of the lamp as an electric heater. 


112 



Tabulation 

Weight of metal vessel .... 

Weight of vessel and water .... 

Weight of water .... 

Temperature of cold water .... 

Temperature resulting .... 

Calories received by vessel .... 

Calories received by water .... 

Calories received, output .... 

Amperage of lamp 

Voltage of lamp 

Wattage of lamp, computed .... 

Time of current flow 

Watt-seconds, joules - 

Calories generated, input .... 

Efficiency of electric heating .... 

Optional 

Obtain the local cost of electric energy per kilowatt-hour 
(lowest rate) and determine the cost of operating the lamp 
for three minutes or the cost of the number of calories re¬ 
ceived. At the same rate compute the cost of obtaining 
1,000,000 calories and compare with the cost of obtaining 
1,000,000 calories with a gas heater determined in a previous 
experiment. 


113 








Experiment 58 — ELECTROMAGNETIC INDUCTION 


( a ) Cause of Induction 

With a piece of insulated wire, No. 18, about six feet in 
length, make a coil of twenty turns by wrapping it around a 
cylinder of about one-inch diameter. Connect the ends of 
the wire or coil to the galvanometer. Move a magnet in 
and out of the coil and note the effect on the galvanometer. 
Note if current is produced when the magnet is not moving. 

State the action or conditions necessary to produce an 
induced current. 

( b ) Magnitude of Induced Electromotive Force 

Note the magnitude of the deflection of the galvanometer 
as a magnet is thrust into or pulled out of the coil. Note the 
magnitude of deflection when the number of lines of force is 
increased by using two magnets with like poles together. 
Note the effect on the magnitude of the deflection when the 
speed of the movement of the magnet is changed. 

State what determines the magnitude of the induced cur¬ 
rent. 

(c) Direction of the Induced Current 

Turn the coil and galvanometer so that you are facing one 
end of the coil. Thrust the N pole of the magnet into the 
coil and determine from the deflection of the galvanometer 
the direction of the current induced in the coil. (The needle 
of the galvanometer mfoves toward the binding post at which 
the current enters.) Record direction as clockwise or counter¬ 
clockwise. Record the direction of current as the magnet is 
pulled out. Repeat using S pole. 

While current is being induced in the coil it is an electro¬ 
magnet. Apply the thumb rule and determine the polarity 
of the end of the coil approached by the N pole of the magnet. 
Explain how this result proves Lenz’s law, 

(i d ) Induction from an Electromagnet 

With a piece of wire about three feet in length make a coil 
of ten turns around a wire nail. Place this coil and nail within 
the other coil. Connect a cell and key in series with the 
inner coil. Face one end of the coils and record the direction 


114 



of the induced current at the instant the key is closed; when 
it is opened. 

Make connections at the battery so that the current will 
flow through the primary in a clockwise direction. Record 
the direction of current in the secondary when the key is 
closed. Repeat with the current counterclockwise in the 
primary. 

State the relative directions of the primary and secondary 
currents. Explain how this is a proof of Lenz’s law. 



Tabulation 
(For c and d) 

. Direction of 

Action Induced Current 

N pole thrust into coil .... 

N pole pulled out of coil .... 

S pole thrust into coil .... 

S pole pulled out of coil .... 

Primary circuit closed .... 

Primary circuit opened .... 

Primary current clockwise .... 

Primary current counterclockwise .... 


Optional 

Determine the effect on the magnitude of the induced 
current when the nail is partly removed and when it is entirely 
removed from the primary coil. Explain. 

115 














Experiment 59 — STUDY OF DYNAMOS 

Study the model and observe the three essential parts of a 
dynamo: the field, or means of producing the magnetic field; the 
armature, or part that rotates and cuts the magnetic lines of force; 
the collectors, or the means of connecting the armature circuit with 
the external circuit. 

There are two types of collectors. To change from one armature 
and collector to the other, turn up or raise the central top screw 
(screw driver not needed) about five millimeters. Then raise the 
armature out of its lower socket and carefully remove it at the side. 
When an armature is replaced, turn down the top screw until the 
armature is held in position and can rotate freely without friction. 

Part I — Magneto 

Place the armature with the two separate rings in position 
and adjust the brushes so that each one is in contact with 
a different ring. Place the permanent bar magnets in the 
clamps with a north and a south pole near the armature. 
The apparatus now represents a magneto. 

(a) Connect the brushes to a galvanometer. Rotate the 
armature very slowly and determine the points at which the 
current reverses. Explain why the current reverses. 

(b) Note the number of times the current reverses in one 
rotation of the armature and state what determines the 
number of alternations per minute or the frequency. 

Part II — Alternating Current Generator 

Remove the bar magnets and place in position the electro¬ 
magnet field coil. In series with the coil place a dry cell, a 
resistance box with the one-ohm plug removed and a key. 
The apparatus now represents a separately excited A.C. 
generator. 

(a) With the key open, rotate the armature and note the 
magnitude of the galvanometer deflection. What is the 
source of the lines of force now being cut? 

(b) Repeat the test with the key closed while the armature 
rotates. What is the cause of the change in the magnitude 
of the current produced? 

(c) Rotate the armature at different speeds. State the 
two factors discovered that determine the magnitude of the 
voltage of a generator. 


116 



Part III — Direct Current Generator—Series-Wound 

Remove the resistance box and cell. Replace the armature 
with the two-ring collector with the armature having a single 
ring divided into two segments (commutator). Connect the 
field coil, the brushes or armature, and the galvanometer or 
external circuit in series to represent a series-wound D.C. 
generator. 

(a) Rotate the armature and note the kind and direction 
of the current produced. Rotate the armature in the other 
direction. 

( b ) Rotate the armature slowly and note what change 
takes place in the commutator when the armature passes 
through the points at which the current was found to alter¬ 
nate in Part I. 

Part IV— .Direct Current Generator — Shunt-Wound 

To represent a shunt-wound generator, connect the field 
coil in parallel with the galvanometer or external circuit so 
that the current from the armature will divide at the brushes, 
a part going through the field and a part through the external 
circuit. 

Have the connections accepted by the instructor. 

Optional 

Make proper connections to have the apparatus operate as 
a compound wound generator. For the series field coil use 
a short piece of drop cord and wind it four or five times around 
the field electromagnet. Have the connections accepted by 
the instructor. 


117 





Experiment 60 — STUDY OF ELECTRIC MOTORS 


As a direct current generator may be used as a direct 
current motor, a motor may be considered as having the same 
three essential parts. 

Part I — Cause of Rotation 

Remove the permanent magnets or electromagnet from 
the field. Use the armature with a commutator and rotate 
it to such a position that it will be diagonal to the base of the 
instrument. Connect a dry cell and key in series with the 
brushes. By means of a compass determine the polarity of 
the armature coil when the key is closed. 

Place the permanent magnets in the clamps with a south 
and a north poW near the armature. Which way does the 
armature rotate when the current is passed? Explain cause 
of rotation. 

Part II — Action of Commutator 

Rotate the armature by hand and observe what happens 
on the commutator at the same time that the pole of the 
armature passes an unlike pole of the field. Explain why 
the armature of a motor continues to rotate. 

Part III — Direction of Rotation 

Remove the bar magnets and place in position the electro¬ 
magnet field coil. Connect field, armature, key and cell in 
series to represent a series-wound motor. 

(a) State the direction of rotation of the armature as 
clockwise or counterclockwise. 

(b) Change the direction of the current by changing the 
battery connections. State direction of rotation. 

(c) Change the direction of the current through the field 
only and state direction of rotation. 

(d) How can the direction of an electric-motor-driven 
vehicle be reversed? 


118 


Part IV — Speed of Rotation 

Set up the apparatus as a shunt-wound motor by connect¬ 
ing the field parallel to the armature or so that the current 
will divide at the brushes, and a part will pass through the 
field and a part through the armature. 

Place a resistance box in the external circuit and note the 
speed of the armature rotation as different resistances (0.1, 
0.3, 0.5, 0.7, ohm) are placed in the circuit. 

Explain how the speed of rotation of an electric motor may 
be controlled. 


Optional 

Back Electromotive Force 

Connect field, armature, key and cell in series as in Part III. 
Make note of the direction of the armature rotation and the 
direction of the battery current through the armature. 

Disconnect the battery and key from the motor and con¬ 
nect the galvanometer as the external circuit. Rotate the 
armature by hand in the same direction that it rotated as a 
motor. Determine by the galvanometer the direction of the 
current produced in the armature. (The pointer of the gal¬ 
vanometer moves toward the binding post where the current 
enters.) 

How is the current generated in the armature and the 
current supplied by the cell related in direction? What is 
the generated pressure called? What effect does it have on 
the current drawn by the motor? 


119 


Experiment 61 — HORSEPOWER OF AUTOMOBILE 


Part I — S.A.E. Formula 

The relative horsepower of automobile engines is often 
determined by means of a formula known as the S.A.E. or 
Society of Automotive Engineers formula: Horsepower 
equals the square of the diameter of the cylinder in inches 
times the number of cylinders divided by 2.5. 

From the Table of Chassis Specifications given in the Ap¬ 
pendix select the car to be studied. Determine the number 
of cylinders and the diameter of cylinder or bore. Substitute 
in the S.A.E. formula and compute the horsepower of the 
engine. 


Part II — Brake Horsepower Formula 

By definition horsepower is obtained by dividing the work 
done per minute (force X distance) by 33,000. In a gas 
engine the force would be the average pressure for the stroke 
times the area of the piston. The distance would be the 
stroke times the number of power strokes per minute, or the 
piston speed in feet per minute divided by four. If this were 
multiplied by the number of cylinders and by the mechanical 
efficiency of the engine, the actual or brake horsepower would 
be obtained. 

(Brake H.P. equals P • A • S • N • E divided by 33,000 X 4.) 

Experiment has shown that the average cylinder pressure 
is 90 lb., to the square inch, and the average efficiency 75 
per cent. Assuming that the car is running at such a velocity 
that the piston speed is 1000 feet per minute, substitute in 
the above equation and solve for horsepower. Compare this 
result with the other and state conclusion. 


120 


Tabulation 
Part I 

Make of car selected .... 

Diameter of cylinder (bore) .... 

Horsepower, S.A.E. formula .... 

Part II 

Pressure, average for stroke .... 

Area of piston, sq. in. .... 

Speed of piston, ft. per min. .... 

Number of cylinders .... 

Efficiency of engine .... 

Horsepower, brake formula .... 

Optional 

The brake horsepower curve shown in Experiment 62 
gives the horsepower at different revolutions per minute 
obtained by actual test on a six-cylinder engine, three and 
one-eighth inch bore, four and one-half inch stroke. 

Apply the S.A.E. formula and compute the horsepower. 

The S.A.E. formula is true only when the piston speed is 
1000 feet per minute. From the stroke compute the revolu¬ 
tions per minute (R.P.M.) of the engine when the piston 
speed is 1000 feet per minute. From the horsepower curve 
determine the horsepower of the engine at that speed. 

Diameter of cylinder (bore) .... 

Number of cylinders .... 

Horsepower, S.A.E. formula _ 

Length of piston movement (stroke) .... 

R.P.M. at 1000 F.P.M. piston speed _ 

Horsepower at above R.P.M. .... 

Compare the horsepower obtained by formula with the 
horsepower obtained by actual test and state conclusion 
concerning the value of the S.A.E. formula. 


121 








Experiment 62 — POWER AND TORQUE CURVES 

Torque is the ability of a force to produce rotation and 
is measured by the product of the force and the perpendicular 
distance from the line of action of the force to the center of 
rotation. 

The unit of torque is the pound foot. It is the torque of a 
force of one pound acting at a distance of one foot. 

In the “brake test” of an engine, the horsepower is ob¬ 
tained by the formula: 


Force X 3.1416 X 2 X Radius X R.P.M. 
33,000 


Horsepower = 


The torque can be obtained from the same test by the 
formula: 

Torque = Force (pounds) X Radius (feet) 

In each of the above formulas obtain a formula for force 
in terms of the other factors. As it is the same force in each 
formula, equate the two quantities and obtain a formula for 
torque in terms of horsepower, R.P.M., and one numerical 
quantity. 

With this formula compute the torque of the Nash 8-80 
engine at each speed given in the following table: 

R.P.M. Horsepower Torque 


600 

900 

1200 

1500 

1800 

2100 

2400 

2700 

3000 

3300 

3500 


18.5 

27.5 

36.5 

45.5 

54.6 
64.0 
73.0 
80.0 
85.0 
87.0 
86.0 


122 







On double-ruled or cross-section paper plot the horsepower 
curve showing the relation between horsepower and the 
number of revolutions per minute. On the same paper plot 
the torque curve showing the relation between the pound- 
feet and the revolutions per minute. 



R. P. M. 


Optional 

From the Table of Specifications given in the Appendix, 
obtain the gear ratio and size of rear tires of the car studied 
above and compute the speed of the car in miles per hour at 
the R.P.M. of the crankshaft when the engine is at its maxi¬ 
mum torque. 


123 



















Experiment 63 — AUTOMOBILE ROAD THRUST 


Power equals force X velocity (ft. per min.). 

Horsepower equals force X velocity divided by 33,000. 

Neglecting the loss in transmission, the power of the driv¬ 
ing or rear wheels of a car will be the same as the engine. If 
the last equation is applied to the rear wheels, the horse¬ 
power of the wheels may be considered as that of the engine 
less ten per cent due to loss of transmission. The velocity 
of the wheel is the given velocity of the car and the force 
factor is the push exerted by the rear tires against the road 
and is called the road thrust. 

From the Table of Chassis Specifications given in the Ap¬ 
pendix, obtain the gear ratio and diameter of rear wheel of the 
car studied in Experiment 62. From the diameter of the 
wheel compute the circumference. From the circumference 
of the wheel compute the number of revolutions per minute 
(R.P.M.) of the rear axle when the car is going 25 miles per 
hour. From the R.P.M. of the axle and gear ratio when in 
high, compute the R.P.M. of the engine at 25 miles per hour. 

Study the horsepower curve of the engine and find H.P. at 
the computed R.P.M. when going 25 miles per hour. Sub¬ 
stitute tire velocity and H.P. of tire in the equation and solve 
for force or road thrust. 

Find the gear ratio of car when in second speed and com¬ 
pute the road thrust at 25 miles per hour. The loss in trans¬ 
mission should now be considered 15 per cent. It is greater 
because of transmission through the countershaft. 

From the results of this study, state the reason for shifting 
to a lower gear when climbing a hill. 


124 


Tabulation 


Position of Shift Lever High Speed Second Speed 

Name of car considered .... 

Gear ratio .... 

Diameter of rear wheel .... 

Circumference of rear wheel .... .... 

R.P.M. of rear axle at 25 M.P.H. .... .... 

R.P.M. of crankshaft at 25 M.P.H. .... .... 

H.P. of engine at above R.P.M. _ .... 

H.P. of rear axles at above R.P.M. _ _ 

Road thrust of wheels at 25 M.P.H. .... .... 

Optional 

Determine the road thrust of the same car when going 
fifty miles an hour in high gear. 


125 










Experiment 64 — AUTOMOBILE ELECTRIC CIRCUITS 

The essential parts of the electric system of an automobile 
may be divided into five distinct circuits: The motor or start¬ 
ing circuit; the ignition primary circuit; the ignition second¬ 
ary circuit; the generator or charging circuit; and the light 
circuits. 

For this study, if the laboratory does not furnish a chart 
of the car of the make desired, the student is to use the chart 
given in the Manual. 

From the chart selected draw the following five distinct 
diagrams each showing one of the five different circuits. In 
these diagrams keep the same relative position of parts as in 
the given diagram. Some wires serve for two or more circuits. 
Label all parts. 


I — Starting Circuit 

Show connections of motor, starting switch, and battery. 

II — Charging Circuit 

Show connections of generator, ammeter, and battery. 

Ill — Ignition Primary Circuit 

Show connections of battery, ammeter, ignition switch, 
primary coil, and timer. 

IV — Ignition Secondary Circuit 

Show connections of secondary coil, distributor, and spark 
plugs. 

V — Light Circuits 

Show connections of battery, ammeter, lighting switch, 
fuses, and lamps. 


126 



Optional 

Explain the purpose of the following instruments in the 
system: Ignition coil; timer; relay; thermostat above 
generator. 


127 




































































































* 



























































PROJECTS 





Project 1 —EFFICIENCY OF GAS WATER-HEATER 


Study carefully the apparatus and note that the water 
may be passed through either heater at will by means of the 
stop-cock back of the heater. 

To test the Sands heater open the stop-cock in water pipe 
back of the heater and close stop-cock back of the other 
heater. Next open the stop-cock near the water faucet at 
the sink. Adjust the faucet so that the rate of flow is a 
stream of water about the size of a lead pencil. 

Light the gas in the Sands heater and open gas-cock fully. 
To avoid an explosion apply match and turn on gas at same 
time. Let the heater operate four or five minutes before 
starting the test. During this time open the cold-water tap 
and let water flow into the sink until thoroughly cold. Just 
before and immediately after the test the temperature of the 
water from the cold-water tap should be obtained. The 
average is to be taken as the temperature of the water before 
heating. 

Determine the amount of water passing through while 
exactly two cubic feet of gas are burned. One student will 
push the pail under the water exit pipe and remove it at the 
signals of a student observing the meter dials. Obtain the 
temperature of the heated water and weight. 

From the weight of water in the pail and the change of 
temperature of the water passing through the heater, com¬ 
pute the number of B.T.U. received from the two cubic feet 
of gas. With the fuel value of gas as 560 B.T.U. per cubic 
foot, compute the input and efficiency of the heater. (See 
Note 2 below.) 

Repeat the experiment in every detail using the Duplex. 
When comparing the efficiency of these two heaters, note 
that one is the coiled pipe type and the other the disc. 

With gas at $.75 per 1000 cubic feet, compute the cost 
of heating 100 lb. of water from 72 to 212 degrees F. in each 
heater. Compute the cost of producing 1000 B.T.U. with 
each heater. 


130 



Tabulation 

Make of Heater Sands Duplex 

1st temperature cold water 
2nd “ “ 

Temperature of water before heating 
Temperature of hot water 
Change in temperature 
Weight of water 

B.T.U. output . 

B.T.U. input .... 

Efficiency .... 

Cost of heating 100 lb. * 

Cost of 1000 B.T.U. 

Note 1: If the hot-water heater at home is to be tested, first 
see that there is no hot water in the tank, then light the burner 
and open some nearby hot-water faucet so that a very small stream 
is flowing. Determine the temperature of the water from the hot- 
water faucet every few minutes and when the temperature becomes 
constant make the test by finding the weight and change of tem¬ 
perature of the water passing through the heater while two cubic 
feet of gas are burned. 

Note 2: If the local fuel value and cost of gas are known, use 
them in place of the value and cost given in the experiment. 


131 















Project 2 —EFFICIENCY OF GAS STOVE 

Weigh the kettle or vessel on the spring balance. Place in 
about two quarts (4 lb.) of water and weigh again. 

Light the gas burner to be tested and regulate the flow of 
gas so that the flame will be of medium size. 

Take the temperature (F.) of the cold water and place the 
kettle on the flame. When exactly one cubic foot of gas has 
been burned to heat the water, remove the kettle and again 
take the temperature. 

Calculate the number of B.T.U. received by the water. 
From the assumption that the heat of combustion of gas is 
560 B.T.U. per cubic foot, determine the efficiency of the 
burner tested. In like manner determine the efficiency of the 
small jet or “simmer.” (See Note 2 in Project 1.) 

To test the oven, light the gas and regulate to a medium 
flame. Have the oven thoroughly heated before making the 
test. Use an open vessel and leave it in the oven while ex¬ 
actly two cubic feet of gas are burned. Make two tests by 
placing the vessel on the upper and lower shelves. 

State your conclusions or comparisons. With gas at $.75 
per 1000 cubic feet what is the cost per 1000 B.T.U. with 
the regular burner? 


132 




Tabulation 



Part Tested 

Regular 0 

DIMMER 

Burner 

Upper 

Oven 

Lower 

Oven 

Wt. of water 

First temp. 

Second temp. 

Output (B.T.U.) 

Gas used 




Input (B.T.U.) 
Efficiency 





Cost of 1000 B.T.U. 

Note: This test may be made at home with the loan of a spring 
balance and a thermometer. Two students will need to work 
together; one to read the meter in the basement as the other works 
at the stove. 


133 





























Project 3 —EFFICIENCY OF DIFFERENT 
KETTLES AND FLAMES 

Weigh the kettle or vessel on the spring balance. Place 
in the vessel about two quarts (4 lb.) of cold water and weigh 
again. (Use a 30-lb. capacity balance.) 

Light the burner and regulate to a maximum flame. Take 
the temperature (F.) of the cold water and place the kettle 
on the flame. When exactly one cubic foot of gas has burned 
to heat the water, take off the vessel and again take the 
temperature. 

Calculate the number of B.T.U. received by the water. 
From the number of B.T.U. (560) supplied by the combustion 
of one cubic foot of gas, determine the efficiency of burner 
and kettle. (See Note 2 in Project 1.) 

Make a similar test with the gas-cock half closed, to find 
the relative efficiency of high and low flames. Make such 
other tests as will enable you to compare the efficiency of 
covered and uncovered vessels and that of aluminum and 
granite vessels. 

State your conclusion or comparisons. With gas at $.75 
per 1000 cubic feet, compute the cost of a 1000 B.T.U. under 
the highest efficiency obtained. 


134 



Tabulation 

Material Granite Granite Granite Aluminum 

Flame High Low Low Low 

Vessel Covered Covered Uncovered Covered 

Weight of water .... .... .... .... 

First temperature .... .... .... .... 

Second temperature .... .... .... .... 

Output (B.T.U.) .... .... .... .... 

Gas used (cu. ft.) .... .... .... .... 

Input (B.T.U.) .... .... .... ... 

Efficiency .... .... .... 

Cost of 1000 B.T.U. 

Note: This test may be made at home with the loan of a spring 
balance and a thermometer. Two students will need to work to¬ 
gether; one to read the meter in the basement as the other works 
at the stove. 


135 


























Project 4 — PRESSURE COOKER 


Part I — Effect of Pressure on Boiling Point 

Place the cooker on the gas stove so that the ring and 
handle are directly in front. Put one quart of water in the 
cooker. Before putting on the cover, wipe dry its lower edge 
and the upper edge of the cooker. Place the cover on care¬ 
fully and screw it down tight. Turn each wing nut a little 
at a time so that the pressure at the contact surfaces is in¬ 
creased uniformly at all points. 

Light the gas and use full flame. The pet-cock on the 
cover should be closed. Watch the thermometer carefully 
and when it passes the ordinary boiling point (212° F. or 
100° C.), open the pet-cock and let the steam and air escape. 
Regulate the gas so that the flame is about one-half of its 
former height. 

When the pressure gauge reads zero, close the pet-cock. 
Now watch the gauge and the thermometer and record the 
temperature at each pound of increase in the pressure up to 
fifteen pounds. If necessary regulate the gas so that the 
increase takes place slowly. When through with the readings, 
turn off the gas and open the pet-cock. When cooled throw 
away the water and wipe dry the cover and vessel. 

Calculate the average increase in temperature when the 
pressure is increased one pound per square inch. Calculate 
the temperature, F. and C., inside the boiler of a steam engine 
when the pressure gauge reads 200 pounds. Measure the 
diameter of the top of the cooker. Calculate the total pres¬ 
sure on the cover at the close of the test. 


136 



Part II — Effect of Pressure on Cooking 

Bring from home two small potatoes of about the same 
size. Any other vegetables may be used if desired. If other 
vegetables are used, consult the instruction book for the 
proper time to cook with 20 pounds of pressure. 

Place a quart of water in an open vessel on one burner. 
Place a pint of water in the cooker on another burner. Heat 
the water to the boiling point in both vessels. Note the 
time and place a potato in each vessel. Immediately place 
the cover on the cooker and screw it down tight. 

Increase the flame so that the pressure will increase rapidly 
to 20 pounds. Now regulate the flame so that the pressure 
will remain constant at 20 pounds. (Be careful not to let the 
pressure get above 25. The safety valve should open at 
that pressure.) 

When the potatoes have been cooking just ten minutes, 
turn off both flames and as soon as possible remove the pota¬ 
toes from the vessels. Compare the condition of the potatoes 
and explain. 


137 




Project 5 —EFFICIENCY OF ELECTRIC PLATE STOVE 


Weigh the vessel on a two-pan balance. Place an extra 
weight of one and one-half pounds on the weight pan. Pour 
water into the vessel until it is again perfectly balanced. 

Set the stove at low heat and connect at the outer socket 
beneath the ammeter on the table switchboard. The am¬ 
meter is now in series with the stove. (See Note below.) 

Place the vessel on the stove and take the temperature of 
the water. Cover the vessel and turn on the current by rais¬ 
ing the lever on the side of the safety-switch box. 

Record readings of the ammeter and voltmeter. To get 
the voltage, place the voltmeter plug in the other socket 
beneath the ammeter. When the vessel has been on exactly 
five minutes open the circuit and record the highest tempera¬ 
ture of the water that can be obtained. 

Calculate the number of B.T.U. received by the water. 
From the relation (1055 watt-seconds equal one B.T.U.) com¬ 
pute the heat developed in the stove during the heating of 
the vessel. Compute the efficiency of the stove. 

Make a similar test to determine the efficiency of the stove 
when set at high heat. Obtain the local price of electrical 
energy per kilowatt-hour (lowest rate) and compute the cost 
of 1000 B.T.U. when set at high heat. 

Note: Many cities require all electric circuits and connections, 
where the voltage is above 25, to be enclosed. The ammeter, 
voltmeter, and safety switch are consequently mounted on a box. 
One of the sockets underneath the ammeter is connected in series 
with the ammeter and switch. The other socket for voltmeter 
connection is connected parallel to the first. 

If all electric connections are made by the student, call 
the instructor before closing the switch. 


138 



Tabulation 

Stove Setting Low Heat High Heat 

Weight of water .... .... 

First temperature .... .... 

Second temperature .... .... 

Output (B.T.U.) .... .... 

Amperage .... .... 

Voltage .... - 

Time of current flow .... .... 

Watt-seconds - .... 

Input (B.T.U.) .... .... 

Efficiency of stove .... - 

Cost of 1000 B.T.U. .... 


139 












Project 6 — EFFICIENCY OF ELECTRIC GRID STOVE 


Weigh the vessel on a two-pan balance. Place an extra 
weight of one and one-half pounds on the weight pan. Pour 
water into the vessel until it is again balanced. 

Set the stove at low heat and connect at the outer socket 
below the ten-ampere-range ammeter on the table switch¬ 
board. The ammeter is now in series with the electric stove. 
(See Note in Project 5.) 

Place the vessel on the stove and take the temperature 
of the water. Cover the vessel and turn on the current by 
raising the lever on the side of the safety-switch box. 

Record the reading of the ammeter and the voltmeter. 
To get the voltage of the circuit, place the terminal of the 
voltmeter cord in the other socket below the ammeter. When 
the vessel has been on exactly five minutes, open the circuit 
and record the highest temperature of the water that can be 
obtained. 

Calculate the number of B.T.U. received by the water. 
From the relation (1055 watt-seconds produce one B.T.U.) 
compute the heat developed in the stove by the current in 
five minutes. Compute the efficiency of the stove. 

Make a similar test to determine the efficiency of the stove 
when set at high heat. Obtain the local price of electrical 
energy per kilowatt-hour (lowest rate) and compute the cost 
of 1000 B.T.U. when set at high heat. 


140 


Tabulation 


Stove Setting Low Heat High Heat 

Weight of water .... 

Temperature of cold water .... 

Temperature after heating .... _ 

Temperature change .... 

Output (B.T.U.) 

Amperage .... 

Voltage _ _ 

Time of current flow .... _ 

Watt-seconds .... _ 

Input (B.T.U.) 

Efficiency of stove .... .... 

Cost of 1000 B.T.U. 


141 










Project 7 —EFFICIENCY OF ELECTRIC 
WATER-HEATER 


Weigh the electric water-heater without the cover on a two- 
pan balance. Place on the weight pan an extra weight of one 
and one-half pounds and pour water into the heater until it 
is again perfectly balanced. 

Connect the heater at the outer socket underneath the five- 
ampere-range ammeter on the table switchboard. The am¬ 
meter is now in series with the heater. (See Note in Project 5.) 

Take the temperature (F.), place on the cover and close 
the circuit for exactly three minutes. (To close the circuit 
raise the lever on the side of the safety switch.) 

During the three minutes record the amperage and the 
voltage. To get the voltage, place the terminals of the volt¬ 
meter cord in the other socket below the ammeter. 

About one minute after opening the circuit take the 
temperature of the water. Watch the thermometer for some 
time and record the highest temperature obtained. 

Calculate the number of B.T.U. received by the water. 
From the relation (1055 watt-seconds are equivalent to one 
B.T.U.), compute the heat developed in the heater. Deter¬ 
mine the efficiency of the heater. 

Make a second test with the cover off. Before making the 
second test, thoroughly cool the heater by letting cold water 
from the tap run into it. 

Obtain the local price of electrical energy per kilowatt- 
hour (lowest rate) and compute the cost of 1000 B.T.U. in the 
test of highest efficiency. 


142 


Tabulation 


Condition of Vessel Cover On 

Weight of vessel 

Weight of vessel and water 

Weight of water 

Temperature of cold water 

Temperature after heating 

Temperature change 

Amperage 

Voltage 

Time of current flow .... 

Watt-seconds 

Input (B.T.U.) 

Output (B.T.U.) 

Efficiency of heater .... 

Cost of 1000 B.T.U. 


Cover Off 


143 










Project 8 — EFFICIENCY OF ELECTRIC 
FIRELESS COOKER 

Weigh the inner vessel of the cooker on the spring balance. 
Put in about three quarts of cold water and weigh again. 
(Use the 30-lb. capacity balance.) 

Connect the cooker at the outer socket beneath the ten- 
ampere-range ammeter on the table switchboard. The am¬ 
meter is now in series with the cooker. When determining 
the voltage, place the voltmeter plug in the other socket 
beneath the ammeter. The voltmeter is now connected 
across the wires leading to the cooker. (See Note in Project 5.) 

Record the temperature of the cold water. Seal the vessel 
and place it in the cooker. Close the safety switch and pass 
current through the cooker exactly ten minutes. 

The ammeter and the voltmeter should be read at the 
beginning and near the end of the ten minutes. If readings 
vary take average. 

Twenty minutes after the current is turned off, open the 
cooker and carefully take the temperature of the water. 
During the twenty minutes make a diagram showing con¬ 
nections of cooker, ammeter, voltmeter, and switch. 

Compute the number of B.T.U. received by the water. 
From the relation (1055 watt-seconds are equivalent to one 
B.T.U.), compute the heat developed in the cooker during the 
ten minutes of current flow. Determine the efficiency of the 
cooker. 

Obtain the local price of electrical energy per kilowatt-hour 
(lowest rate) and compute the cost of 1000 B.T.U. 


144 



Tabulation 

Weight of inner vessel 
Weight of vessel and water 
Weight of water 
Temperature of cold water 
Temperature after heating 
Temperature change 
Amperage 
Voltage 

Time of current flow 
Watt-seconds 
Input (B.T.U.) 

Output (B.T.U.) 

Efficiency of cooker 
Cost of 1000 B.T.U. 


145 











Project 9 — ELECTRIC LIGHTS — COST 
PER C.P. HOUR 

Place the standard incandescent light at one end of the 
optical bench. Place the lamp to be tested at a distance 
100 centimeters from the standard. Slide the photometer 
back and forth between the lights until a position is found 
where the screen is equally illuminated on both sides. 

As it is difficult to set the photometer at its correct posi¬ 
tion, several trials should be made and the average recorded. 
One method is to place the photometer too far to the right 
and move it to the left until the oiled.spot is apparently 
equally illuminated on each side. Find a second point by 
approaching from the left. A point midway between these 
two points is to be recorded as the correct position of the 
photometer. 

Measure the distance from the screen of the photometer 
to the center of the standard and from the screen to the 
center of the lamp tested. Compute the candle power of the 
lamp. 

Test such lamps that will enable you to compare the rela¬ 
tive cost per candle-power-hour of low and high wattage 
lamps; of frosted and clear lamps; of fresh and used lamps; 
of Mazda B and Mazda C lamps. 

To determine the exact wattage of the lamp tested use a 
one-ampere meter of the table switchboard. To get the 
voltage place the terminals of the voltmeter cord in the other 
socket below the ammeter. When reading the ammeter dis¬ 
connect the voltmeter. (See Note in Project 5.) 


146 


From the wattage and the candle power compute the watts 
per candle power. With electrical energy at ten cents per 
kilowatt-hour, compute the cost of using each lamp for one 
hour. From this cost and the candle power of the light, com¬ 
pute the cost per candle-power-hour for each lamp. State 
conclusions. 


Tabulation 

Lamp Tested . 

Distance (phot, to lamp) . 

Distance (phot, to stand.). 

Candle power of lamp . 

Amperage . 

Voltage . 

Wattage (computed) . 

Watts per candle power . 

Cost of lamp per hour . 

Cost per C.P. Hour . 


147 






















Project 10 — HOUSEHOLD LAMP CONNECTIONS 

In some cities it is required that all electric connection and circuits 
be enclosed, if the voltage is above 25. The box shown in the picture 
is a suggestion of how to meet those requirements and still give the 
student the experience of making and testing the different kinds of 
connections. 

The door of the box cannot be opened without disconnecting it 
from the switchboard. When the lamp receptacles have been 
connected as desired and the connection approved by the instructor, 
then close the door and connect the circuit to the switchboard. The 
lamps must be placed in the receptacles after the door is closed. 

If enclosed circuits are not required and all connections are made 
by the student, connect first the receptacles as desired and then 
connect in series with the ammeter. The voltmeter should be 
connected to the two points whose difference of pressure is to be 
measured. 


Part I — Parallel Connections 

Connect one lamp in series with the ammeter. Connect 
the voltmeter across the terminals of the source of the cur¬ 
rent. The voltmeter should be disconnected when reading 
the ammeter. Connect two lamps in parallel and again read 
the ammeter and the voltmeter. 

If a residence had twenty such lamps connected in parallel, 
compute the amperage and the voltage if all lamps were in 
service. At ten cents per kilowatt-hour, compute the cost 
of running all lamps one hour. 

Part II — Series Connections 

Connect two lamps in series and determine the amperage. 
Determine as before the voltage of the source and also the 
voltage across the terminals of one lamp. Note the intensity 
of the light. 

Compute the voltage necessary at the source to cause the 
two lamps to give their normal amount of light. Compute 
also what the ammeter would then read. 

If a residence had twenty such lamps connected in series, 
compute the amperage and the voltage if all lamps were in 
service. At ten cents per kilowatt-hour, compute the cost 
of running all lamps one hour. 

148 



Tabulation 

Part I — Parallel Connections 

Amperage of one lamp 
Voltage for one lamp 
Amperage of two lamps 
Voltage for two lamps 
Amperage of twenty lamps 
Voltage for twenty lamps 
Cost of twenty lamps for one hour 


Part II — Series Connections 

Amperage obtained with two lamps 
Amperage necessary for two lamps 
Amperage for twenty lamps 
Voltage of source 
Voltage of one lamp 
Voltage necessary for two lamps 
Voltage for twenty lamps 
Cost of twenty lamps for one hour 


149 

















Project 11 —HEAT AND LIGHT RADIATIONS 
OF LAMPS 


Weigh the calorimeter on a platform balance to the nearest 
tenth of a gram. Weigh the vessel about one-half full of 
water, six or eight C. degrees below room temperature. 

By means of a universal clamp support an electric-light 
socket in a vertical position so that the lamp can be raised or 
lowered on the support rod. Place in the socket a 60-watt 
lamp. 

Connect the lamp to the outer socket beneath the one- 
ampere ammeter on the switchboard. The lamp is now in 
series with the ammeter. To determine the voltage, place 
the plug connected to the voltmeter in the other socket below 
the ammeter. (See Note in Project 5.) 

Lower the lamp into the calorimeter until the brass base 
is just above the surface of the water. Take the temperature 
(C.) of the water and immediately turn on the current. 
Record the amperage and voltage. At the close of exactly 
five minutes turn off the current. Stir the water with the 
thermometer and record the highest temperature obtained. 

Compute the number of calories received by the water and 
by the vessel. (Sp. heat of the vessel, 0.1.) 

Repeat the experiment, using the glass beaker in place of 
the calorimeter. (Sp. heat of glass, 0.2.) 

From the amperage, voltage, and time compute the number 
of watt-seconds or joules. From the heat equivalent of an elec¬ 
tric current (one joule is equal to 0.24 calorie), compute the 
number of calories generated by the current in five minutes. 

An electric light radiates both heat and light energy. 
With the metal vessel both heat and light energies are con¬ 
verted into heat. With a glass vessel the light energy passes 
through and only the heat energy is absorbed by the water 
and the vessel. Thus the difference in the number of calories 
received, when using glass and metal vessels, is a measure of 
the light energy that is transformed into heat or the output 
of the lamp in light energy. Compare this with the total 
input or the calories generated by the current, and compute 
the percentage of the electrical energy of the current a lamp 
converts into light. 


150 



Tabulation 

Vessel Used Calorimeter Glass Beaker 

Weight of vessel 

Weight of vessel and water .... 

Weight of water 

Temperature of cold water 

Temperature after heating 

Calories received by water 

Calories received by vessel .... 

Calories received, total .... .... 

Amperage of lamp .... 

Voltage of lamp .... 

Time of current flow (seconds) .... 

Watt-seconds, joules .... 

Calories generated by current .... 

Calories (heat and light energy) .... 

Calories (light energy) .... 

Percentage of light energy .... 


151 















Project 12 — GAS FLATIRON 


Remove the top from the gas flatiron. Turn on the gas 
and immediately light it in the iron. Adjust the gas supply 
until the gauge reads about six cubic feet per hour. 

If not familiar with the usual method of determining the 
proper temperature for ironing, give the iron five or six 
minutes to heat before beginning to iron. 

During the time that the iron is heating, thoroughly soak 
the towel and then wring as dry as possible. Weigh on the 
platform balance to the nearest tenth of a gram. 

While one student is ironing the other should determine 
by means of a stop-watch the exact time that the iron is in 
contact with the towel. The watch is operated by moving 
the side piece. It records the time for the performance, ex¬ 
cluding interruptions. If the iron is lifted from the towel the 
watch should be stopped until the ironing is continued. 

Iron rapidly so as to waste as little heat as possible until 
the towel is entirely dry. Turn off the gas immediately at 
the close of the test. Weigh the ironed towel to the tenth of a 
gram. 

Compute the efficiency of the iron. To determine the out¬ 
put of the iron in calories, compute the heat necessary to 
change the water of the towel (loss in weight) from room 
temperature to boiling point (C.) and to change it into vapor. 
To find the input or heating power of the gas used during the 
test, consider the heat of combustion of gas as 141,400 
calories per cubic foot. 

Each student should iron a towel for the data of his own 
individual record. Obtain the local price of gas per 1000 
cubic feet and compute the cost of ironing the towel. 


152 





Tabulation 

Weight of damp towel 
Weight of ironed towel 
Weight of water evaporated 
Room temperature (C.) 

Calories — to raise temperature 

Calories — to evaporate 

Output — calories 

Gauge reading (cu. ft. per hr.) 

Time of ironing 

Cubic feet of gas used 

Input — calories 

Efficiency of iron 

Cost of ironing the towel 


153 









Project 13 —ELECTRIC FLATIRON 


Connect the iron to the outer socket below the five-ampere- 
range ammeter on the table switchboard. To determine the 
voltage connect the terminal of the voltmeter cord to the 
other socket below the ammeter. (See Note in Project 5.) 

If not familiar with the usual method of determining when 
the iron is at the proper temperature for ironing, give the 
iron five or six minutes to heat before starting to iron. 

During the time that the iron is heating, thoroughly soak 
the towel and wring as dry as possible. Weigh the towel on 
the platform balance to the nearest tenth of a gram. 

While one student is ironing the other should determine 
by means of a stop-watch the exact time that the iron is in 
contact with the towel. 

The watch is operated by moving a side piece. It records 
the total time used for the performance, excluding interrup¬ 
tions. If the iron is lifted from the towel, the watch should 
be stopped until the ironing is continued. 

Iron rapidly so as to waste as little heat as possible until 
the towel is thoroughly dry. Open the safety switch im¬ 
mediately at the close of the test. Weigh the ironed towel to 
the tenth of a gram. 

Compute the efficiency of the iron. To determine the out¬ 
put of the iron in calories, compute the heat necessary to 
change the water of the towel (loss in weight) from the room 
temperature (C.) to the boiling point and to evaporate the 
water. To find the input or heating power of the current for 
the time used, apply the formula (one calorie equals 4.17 
watt-seconds). 

Each student should iron a towel for the data of his own 
record. Obtain the local price of electrical energy per kilo¬ 
watt-hour (lowest rate) and compute the cost of ironing the 
towel. 


154 



Tabulation 

Weight of damp towel 
Weight of ironed towel 
Weight of water evaporated 
Room temperature (C.) 
Calories to raise temperature 
Calories to evaporate 
Output (calories) 

Reading of ammeter 
Reading of voltmeter 
Time of ironing 
Watt-seconds 
Input (calories) 

Efficiency of iron 
Cost of ironing towel 


155 









Project 14 — HORSEPOWER AND EFFICIENCY 
OF ELECTRIC MOTOR 


In an alternating-current circuit containing coils the true 
power is obtained by multiplying the apparent power (prod¬ 
uct of volts times amperes) by some number, called the power 
factor, which can. be obtained from the manufacturer. The 
power factor of the one-fourth horsepower Western Electric 
induction-repulsion motor, type RSA, is 0.60. 

To determine the horsepower of the motor use the device 
known as the Prony brake. As the shaft rotates the differ¬ 
ence between the two balances will give the pounds of pull on 
the face of the pulley. This force or pull will be exerted each 
minute through a distance equal to the circumference of the 
pulley times the number of revolutions per minute. From 
the force and the distance, the work done per minute and the 
horsepower can be computed. 

Connect the motor to the outlet below the ten-ampere- 
range ammeter on the switchboard. Place the terminal of the 
voltmeter cord in the other outlet below the ammeter. The 
ammeter is now connected in series and the voltmeter in 
parallel with the motor. Start the motor by raising the lever 
on the side of the safety-switch box. (See Note in Project 5.) 

While the motor is running, place the belt about the pulley 
and raise the balances until the difference of readings is about 
nine pounds (full load). 

One student should determine by means of the speed indi¬ 
cator the number of revolutions made per minute. At the 
same time the second student should read and record the 
amperage and voltage. Watch the meters and balances and, 
if they vary during the test, take the average reading. 

Immediately at the end of the minute stop the motor. The 
motor should not be left running under load any longer than 
is necessary, as the friction will soon destroy the belt and the 
motor may be injured by overheating. 

Measure the circumference of the pulley by means of a rope 
of the same size as the rope used for the belt. 

156 


Compute the work done per minute and the horsepower 
(output) of the motor. From the amperage, voltage and 
power factor, compute the input in watts and in horsepower. 
Determine the efficiency of the motor. 

Make a second test with a smaller load, with a difference 
of balance readings of about six pounds. 


Tabulation 

Load during Test Full Load Part Load 

Voltmeter reading .... .... 

Ammeter reading .... .... 

Power factor of motor .... .... 

Input in watts .... .... 

Input in horsepower .... .... 

Balance reading No.l _ _ 

Balance reading No. 2 - - 

Force on belt (pounds) - - 

Circumference of pulley - - 

No. of revolutions per minute .... - 

Distance in feet per minute .... - 

Foot pounds per minute .... - 

Output in horsepower - - 

Efficiency of motor - - 


157 










Project 15 — HORSEPOWER AND 
EFFICIENCY OF WATER MOTOR 


To start the motor care must be taken to turn on the water 
very slowly. When shutting off the water to stop the motor 
the same care must be taken to do it slowly. 

To determine the horsepower of the motor use the device 
known as the Prony brake. As the shaft rotates the differ¬ 
ence between the two balances will give the pounds of pull on 
the face of the pulley. This force or pull will be exerted each 
minute through a distance equal to the circumference of the 
pulley times the revolutions per minute. The work done in 
one minute will be this pull times the distance per minute, 
from which the horsepower can be computed. 

When the motor has reached full speed, gradually raise the 
spring balances until the load or pull on the belt is as great as 
the motor can work. One student should determine by means 
of a speed indicator the number of revolutions made in one 
minute. During this time the second student should place 
a vessel under the outlet and catch the flow for one-half of 
a minute and record the reading of the pressure gauge. 

Determine the circumference of the pulley by means of a 
rope of the same size as that used for the belt. From the cir¬ 
cumference, the number of revolutions and the brake pull, 
compute the work done per minute and the horsepower of 
the motor. 

The input or work done on the motor is called fluid work 
and is equal to the pressure or force times the distance the 
water flows per minute. Since the gauge gives the pressure 
per square inch, the size of the pipe may be considered as one 
square inch in cross-section. The volume in cubic inches 
flowing per minute will then give the distance in inches that 
the water flows per minute. 

Weigh the water that passed through the motor during 
the half minute of test and compute its volume in cubic 
inches. Express the distance the water flows per minute in 
feet and compute the input or work done on the motor. 
Compare with the output or work done by the motor on the 
brake and determine the efficiency of the motor. 

158 



Tabulation 

First balance reading .... oz. 

Second balance reading .... oz. 

Output force (dif. of readings) .... lb. 

Circumference of pulley .... in. 

Number of revolutions per minute .... 

Output distance .... ft. 

Output (foot pounds per minute) .... 

Horsepower of motor .... 

Input force (water pressure per sq. in.) .... lb. 

Weight of water per minute .... lb. 

Volume of water per minute -cu. in. 

Input distance (velocity of water) -ft. 

Input (foot pounds per minute) .... 

Efficiency of water motor .... 


159 













Project 16 — HORSEPOWER AND 
EFFICIENCY OF GAS ENGINE 


Study carefully the directions and have thoroughly in mind all 
that is to be done before starting the experiment. 

The efficiency of an engine is the ratio of the work developed at 
the crankshaft to the work or energy supplied to the engine in the 
fuel. The heat value of the gas here used is to be taken as 560 B.T.U. 
per cubic foot. Knowing the gas consumed per minute and the 
mechanical equivalent of heat, the input can be computed. 

To determine the brake horsepower use the device known as the 
Prony brake. As the shaft rotates the difference between the two 
balances will give the pounds of pull on the face of the pulley. This 
force or pull will be exerted each minute through a distance equal 
to the circumference of the pulley times the revolutions per minute. 
The work done in one minute will then be this pull times the dis¬ 
tance per minute, from which the horsepower can be computed. 

When ready to start the engine, call the instructor. Have 
the water jacket filled within an inch or two of the top; 
open full the gas-cock beneath the gas meter; close the elec¬ 
tric switch on the side of the battery box. 

To crank the engine turn the wheel back as far as you can 
without effort and then with a quick movement clockwise 
turn it through one compression and immediately let loose 
the handle. If it does not start, repeat; but under no con¬ 
sideration keep hold of the handle for more than one revolution. 

When the engine is running smoothly raise the spring bal¬ 
ances until the difference of the readings is about 25 pounds. 
One student should determine by means of the speed indicator 
the number of revolutions made in one minute. At the same 
time the second student should observe the one-half cubic 
foot dial of the gas meter and determine the volume of gas 
used per minute. Record the readings of the two spring 
balances and stop the engine by opening the electric switch. 
Close the gas-cock. The engine should not be left running 
under load any longer than necessary, as the friction would 
soon destroy the belt. 

Measure the diameter or circumference of the pulley wheel 
and compute the work done per minute or the brake horse¬ 
power. From the volume of gas consumed compute the 

160 


energy given to the engine per minute. Determine the effi¬ 
ciency of the engine. Make a second test with a smaller 
load, with a difference of balance readings of about 15 pounds. 



Tabulation 

Load during Test Full Load Part Load 

Circumference of pulley .... .... 

First balance reading .... .... 

Second balance reading .... _ 

Force (pull of belt) .... .... 

Revolutions per min. .... _ 

Distance (ft. per min.) _ _ 

Work per min. (ft. lb.) .... .... 

Horsepower of engine .... .... 

Gas used (cu. ft.) - - 

Heat equivalent of gas used .... .... 

Mech. equivalent of gas used .... .... 

Efficiency of gas engine - - 


161 



















Project 17 —STUDY OF AUTOMOBILE ENGINE 


Remove the cylinder-head casting from the engine. (When 
a mechanism is to be taken apart, carefully observe the ar¬ 
rangement and parts as they are removed so that they may 
be properly reassembled at close of study.) 

1. Record the make of car and the number of cylinders. 
Measure and record the bore and stroke. 

2. Compute the displacement of the engine. The displace¬ 
ment of one cylinder is the cross-section area times the stroke. 

3. Record the type of valve: Sleeve or poppet. 

4. If poppet, classify the engine according to the location 
of valves. 

5. Determine which is the intake valve and which is the 
exhaust by the difference in the cams. 

6. Record the number of main bearings on the crankshaft. 
Is the crankshaft equipped in any way to reduce vibrations? 

7. Determine the type of front end drive — or how the 
camshaft is driven by the crankshaft. By chain or by gears? 
If gears, spur or helical? 

8. Record the make of carburetor and determine, if pos¬ 
sible, the method of preventing rich mixture as speed is 
increased. 

9. Has the carburetor a choke or primer for making mix¬ 
ture richer when starting? 

10. Is the carburetor equipped with any air-heating de¬ 
vice? 

11. Is the intake manifold equipped with hot-spot, hot- 
water jacket, or exhaust-gases jacket? 

12. Determine if the exhaust manifold is single or double 
and if equipped with a cut-out. 

13. Classify the cooling system: Air or water; thermo¬ 
syphon or pump. If the pump system, is there a thermostat 
control? 


162 


14. Classify the oiling system: Splash; pressure; pressure- 
splash. 

15. Explain how the following parts are lubricated: Cylin¬ 
der walls; camshaft bearings; crankshaft bearings; connect¬ 
ing rod bearings. 

Note: If the laboratory is not provided with an automobile 
engine, most of the above questions may be answered for the home 
car by a study of the engine and the Book of Instructions furnished 
with the car. 


163 


Project 18 —STUDY OF AUTOMOBILE CHASSIS 


1. Determine and record the make and model of the 
laboratory chassis or the car to be studied. 

2. Measure the wheel base on each side of the car by 
measuring the distance from center of rear axle to center of 
front axle. 

3. Set the front wheels for a straight, forward movement 
and check the alignment: 

(а) Camber. Measure the distance between the two front- 
wheel rims at the top and at the bottom. Record difference 
as the camber. 

(б) Toe-in. Measure the distance from rim to rim at the 
front and at the rear of the front wheels at the level of the 
hub. The difference is the toe-in. 

4. Classify the clutch: (a) Cone or disc; ( b ) Single disc 
(plate) or multiple; (c) Run dry or in oil. 

5. From a study of the gear set determine the type of 
shift: Universal or standard. Record number of speeds 
forward. 

6. Observe the number and location of the universals. 
Classify as fabric or metal. 

7. Is the propeller shaft hollow or solid? Is it exposed or 
enclosed in a tube (torque tube)? 

8. Determine the type of rear axle: Semi-floating; if the 
weight of the car rests on the axle or if the bearings are 
between axle and housing. Floating; if the axle is not under 
the strain of the weight of the car or if the bearings are be¬ 
tween housing and hub of wheel. 

9. Determine the type of rear axle bearings: Ball; roller; 
tapered cone (Timken). 

10. Determine the type of rear drive: Spring; if the push 
of the rear wheels against the frame of the car is through the 
springs. Torque tube; if the tube is fastened rigidly to the 
frame. Hotchkiss; if there are two universals. 

11. State the number and type of brakes; the location 
(internal or external) of the hand and of the foot brakes. 

164 


12. Classify the rear springs: Semi-elliptic; three-quarter 
elliptic; full elliptic; cantilever; platform. 

13. Give location of tank and state method of getting the 
gasoline from tank to carburetor (feed system): Gravity; 
pressure; vacuum tank. 

14. Determine the type of motor drive or the method of 
connecting the starting motor to the crankshaft when start¬ 
ing: Bendix drive; pedal mechanism; chain connection. 



Note: If the laboratory is not equipped with an automobile 
chassis, make a study of the home car. If questions cannot be 
answered by observation, consult the Book of Instructions supplied 
with the car. 


165 



Project 19 — AUTOMOBILE GEAR RATIOS 


By gear ratio of an automobile is meant the number of 
revolutions of the crankshaft of the engine to one revolution 
of the rear-axle shafts. 

If the transmission gears are placed in “high” or direct 
drive, the crankshaft of the engine is connected directly to 
the propeller shaft and the only reduction in the number of 
revolutions will be in the differential. 

Count the number of teeth in the ring gear and in the drive 
pinion gear of the differential and determine the number of 
times the crankshaft revolves to one revolution of the rear- 
axle shafts. 

To determine the gear ratio when in “second,” place the 
shift lever in intermediate or second and then remove the top 
of the gear-set box. Count the number of teeth in the clutch- 
shaft gear and in the constant mesh gear and determine the 
ratio of rotations of clutchshaft to countershaft. 

Count the number of teeth in the countershaft second or 
intermediate gear and in the intermediate shifter gear on the 
driveshaft. Determine the ratio of rotations of the counter¬ 
shaft to the driveshaft. 

From these two ratios and the ratio of ring gear to drive- 
pinion gear in the differential compute the number of revolu¬ 
tions of the crankshaft to one revolution of the rear-axle 
shafts or the gear ratio when in “second.” 

Count the number of teeth in the countershaft low gear 
and in the shifter low gear on the driveshaft. Compute as 
before the number of revolutions of the crankshaft to one 
revolution of the rear-axle shafts or the gear ratio when in 
“low.” 

Note: If the gear ratios of the home car are to be determined, 
jack up one of the rear wheels and set the shift lever in the gear or 
speed to be tested. Count the number of revolutions of the starter 
crank necessary to rotate the rear wheel through one revolution. 
Multiply this number by two, as only one wheel is rotating. 

166 



1 
2 

3 

4 

5 

6 

7 

8 

Tabulation 

Number of teeth in ring gear 
Number of teeth in drive pinion 
Gear ratio in high 

No. of teeth in clutchshaft gear 
No. of teeth in countershaft gear 
Ratio — clutchshaft to countershaft 
No. of teeth in countershaft second gear 
No. of teeth in driveshaft second gear 
Ratio — countershaft to driveshaft 
Gear ratio in second 

No. of teeth in countershaft low gear 
No. of teeth in driveshaft low gear 
Ratio — countershaft to driveshaft 
Gear ratio in low 


Shifter Lock Adjustment 
Shifter Bar 
Clutchshaft Gear 
Constant Mesh Gear 
Second Speed Gear 
First Speed Gear 
Reverse Speed Gear 
First and Reverse Shifter Gear 


9 —- Second and High Shifter Gear 

10 — Transmission Shaft 

11 — Shifter Fork 

12 — Clutchshaft Bearing 

13 — Transmission Shaft Bearing 

14 — Adjusting Shims 

15 — Speedometer Drive Gear 

16 — Speedometer Drive Gear 


167 










Project 20 — AUTOMOBILE ELECTRIC SYSTEM 


1. Determine if the car is equipped with a single or two- 
unit electric system. If the starting motor and generator 
are separate instruments, it is two-unit. A single instrument 
may serve both purposes and is called a starter-generator. 

2. Classify the ignition system as battery or magneto. 
Determine by the source of the current used for ignition. 

3. Raise the cap from the distributor and determine the 
direction of rotation of the arm. From the rotation and the 
connections to the spark plugs, determine the firing order. 
Cylinder nearest to the radiator is No. 1. 

4. Move the spark lever or control and discover its action 
on the distributor. Explain how it changes the time of the 
spark. 

5. Discover, if possible, the position of the “cut-out” or 
device for connecting or disconnecting generator at different 
speeds. 

6. Discover, if possible, if there is a “third brush” on the 
generator or a thermostat in its circuit. These are devices 
(regulators) for preventing the generator from producing 
excessive current at high speeds. 

7. Determine the method of dimming the headlights. 
The more common methods are: Place extra resistance in 
the circuit; change the connection of the lamps from parallel 
to series; place auxiliary bulbs in the head lamps. 

8. Draw a diagram of the starter circuit showing connec¬ 
tion of motor, starting switch, and battery. Diagrams will 
have greater value if the parts connected have the same rela¬ 
tive position in the drawing as on the car. 

9. Draw a diagram of the charging circuit showing connec¬ 
tion of generator, ammeter, and battery. 

10. Draw a diagram of the ignition primary circuit show¬ 
ing connection of battery, ammeter, ignition switch, primary 
coil, and timer. 


168 


11. Draw a diagram of the ignition secondary circuit, 
showing connection of secondary coil, distributor, and spark 
plugs. 

12. Draw a diagram of the lighting circuits, showing con¬ 
nection of battery, ammeter, lighting switch, fuses, head and 
rear lamps. 

Note: If a study is made of the home car, secure the Book of 
Instructions and Wiring Chart from the dealer. 


169 



Project 21 —FACTORS DETERMINING H.P. OF 
AUTOMOBILE ENGINES 


Part I — Relation of H.P. to Piston Displacement 

From the tables of automobile specifications given in the 
Appendix tabulate several six-cylinder engines and compute 
the horsepower per cubic inch of piston displacement for each 
engine when running at 1800 revolutions per minute. 


Tabulation 

Make and No. of Piston H.P. at H.P. per Cu. In. 

Model Cylinders Displacement 1800 R.P.M. Displacement 


etc. 

Compute the average H.P. per cubic inch of displacement. 

Do the results obtained indicate a definite relation be¬ 
tween the horsepower and the piston displacement or size 
of engine? 


Part II — Relation of H.P. to the Number of 
Cylinders 

Make a similar table of several eight-cylinder engines and 
compute the horsepower per cubic inch of displacement 
when engine is running at 1800 revolutions per minute. 
Compute the average ratio and compare with the average 
of the six-cylinder engines. 

Make a similar study and comparison with the sixteen- 
cylinder engines. 

Do the results obtained indicate any definite relation be¬ 
tween the horsepower and the number of cylinders? 


170 










Part III — Relation of H.P. to the Type of Engine 

Compute the horsepower per cubic inch of displacement 
when running 1800 revolutions per minute of such engines 
that will determine if there is any advantage in the following 
comparisons: 

(a) Long and short stroke in comparison with bore 

(b) Location of valves (Over-head and L-head) 

(c) Type of cooling system (Air and Water) 

Part IV — Comparison of the Horsepower of 
Different Engines at the Same Car Speed 

On double-ruled or cross-section paper, plot the six 
different horsepowers at the revolutions per minute given 
in the Appendix and draw the horsepower curve of the engine 
of each car to be compared. 

Obtain the diameter of the tires, compute the circumfer¬ 
ence of the wheels and determine the number of revolutions 
per minute of the rear wheels when the car is going 30 miles 
per hour. Obtain the gear ratio of the car and determine 
the revolution per minute of the crankshaft at 30 miles per 
hour. 

From the horsepower curve of the engine determine the 
horsepower at the R.P.M. of the crankshaft when the car 
is going 30 miles per hour. 


Tabulation 

Make and model of car .... 

Diameter of tire .... 

Circumference of wheel .... 

R.P.M. of rear axle .... 

Gear ratio in high .... 

R.P.M. of crankshaft .... 

H.P. at 30 mi. per hr. .... 


171 














APPENDIX A 


TABLE 1 

Numbers and Formulas 

7 r = 3.1416 
t r 2 = 9.86965 

Circumference of circle = 27 rR 
Area of circle = ttR 2 
Surface of sphere = 7rD 2 
Volume of sphere = ±tR 3 
Volume of cylinder = ttR 2 H 


1 rod = 

16| feet 


1 cu. ft. = 1728 cu. in. 


1 mile = 

320 rods 


1 bushel =2150 cu. in. 


1 mile = 

5280 feet 


1 gallon = 231 cu. in. 


1 sq. ft. = 

144 sq. in. 


1 H.P. = 746 watts 


1 acre = 

160 sq. rd. 


1 B.T.U. = 252 gram-calories 

640 acres = 

1 sq. mi. 


1 B.T.U. = 778 foot pounds 

1 B.T.U. = 1055 watt-seconds 
1 calorie =4.17 watt-seconds 




TABLE 

2 



English and Metric Equivalents 


1 meter = 

39.37 in. 


1 inch = 2.5400 cm. 


1 meter = 

3.2809 ft. 


1 foot = 30.480 cm. 


1 kilometer = 

0.6214 mi. 


1 mile = 1.6093 km. 


1 sq. cm. = 

0.1550 sq. in. 


1 sq. in. = 6.4515 sq. cm. 

1 sq. m. = 

10.764 sq. ft. 


1 cu. in. = 16.387 cu. cm. 

1 cu. cm. = 

0.0610 cu. in. 


1 fluid oz. = 29.571 cu. cm. 

1 cu. m. = 

1.3080 cu. yd. 


1 dry qt. = 1.101 liter 


1 liter = 

0.9083 dry qt. 


1 grain = 0.0648 gm. 


1 gram = 

0.0353 oz. 


1 pound = 453.59 gm. 


1 kilogram = 

2.2046 lb. 


1 ounce = 28.349 gm. 




TABLE 

3 


Specific Gravity — 

Grams per Cubic Centimeter 


Alcohol. 

. 0.83 


Iron, cast. 

7.23 

Aluminum. . . 

. 2.67 


Iron, wrought. 

7.78 

Ash, dry. 

. 0.69 


Lead, cast. 

Maple. 

11.36 

Asphalt. 

. 2.50 


0.76 

Brass, cast.. . 

. 8.40 


Marble. 

2.72 

Brick. 

. . . . 1.60-2.00 


Mercury. 

13.60 

Chalk. 

.... 1.80-2.80 


Oak, red. 

0.85 

Coal. ....... 

. . . . 1.26-1.80 


Oak, white. 

0.78 

Copper, cast. 

. 8.83 


Pine, white. 

0.55 

German silver 

. 8.43 


Porcelain. 

2.38 

Glass, crown. 

. 2.52 


Quartz. 

2.65 

Granite. 

. 2.65 


Steel. 

7.82 

Ice. 

. 0.92 


Tin, cast. 

7.29 




Walnut. 

0.68 




Zinc, cast 

7.00 


172 





























TABLE 4 


Decimal Equivalents for Fractions of Inch 


Fractions 

64ths 

Decimal 

Fractions 

64ths 

Decimal 


1 

0.0156 


33 

0.5156 


2 

0.0313 


34 

0.5313 


3 

0.0469 


35 

0.5469 

TV 

4 

0.0625 

9 

1 6 

36 

0.5625 


5 

0.0781 


37 

0.5781 


6 

0.0938 


38 

0.5938 


7 

0.1094 


39 

0.6094 

1 

8 

0.1250 

5 

8 

40 

0.6250 


9 

0.1406 


41 

0.6406 


10 

0.1563 


42 

0.6563 


11 

0.1719 


43 

0.6719 

TE 

12 

0.1875 

1 1 

TV 

44 

0.6875 


13 

0.2031 


45 

0.7031 


14 

0.2188 


46 

0.7188 


15 

0.2344 


47 

0.7344 

1 

4 

16 

0.2500 

3 

4 

48 

0.7500 


17 

0.2656 


49 

0.7656 


18 

0.2813 


50 

0.7815 


19 

0.2969 


51 

0.7969 

5 

TV 

20 

0.3125 

1 3 

TV 

52 

0.8125 


21 

0.3281 


53 

0.8281 


22 

0.3438 


54 

0.8438 


23 

0.3594 


55 

0.8594 

3 

8 

24 

0.3750 

7 

¥ 

56 

0.8750 


25 

0.3906 


57 

0.8906 


26 

0.4063 


58 

0.9063 


27 

0.4219 


59 

0.9219 

TV 

28 

0.4375 

1 5 

T¥ 

60 

0.9375 


29 

0.4531 


61 

0.9531 


30 

0.4688 


62 

0.9688 


31 

0.4844 


63 

0.9844 

1 

32 

0.5000 

1 6 

TV 

64 

1.0000 


TABLE 5 

Coefficient of Sliding Friction 


Brass on cast iron. 0.19 

Iron on iron. 0.14-0.20 

Iron on ice. . . . 0.016-0.032 

Oak on oak. 0.32-0.48 

Leather on oak . . 0.27-0.38 

Hemp on oak, dry. 0.53 

Hemp on oak, wet — 0.33 


Leather on metals, dry. 0.56 

Leather on metals, wet. 0.36 

Leather on metals, oily. 0.15 

Metals on oak, dry.... 0.50-0.60 

Metals on oak, wet.0.24-0.26 

Iron on stone. 0.30-0.70 

Wood on stone. 0.40 


173 











TABLE 6 


Strength of Metals — Pounds per Square Inch 


Aluminum wire.... 

Brass wire. 

Bronze wire. 

Copper, hard drawn 

Gold wire. 

Iron, cast. 

Iron, hard drawn... 
Iron, annealed. 


30000-40000 

50000-150000 

95000-140000 

60000-70000 

20000 

13000-33000 

80000-120000 

50000-60000 


Platinum wire .... 50000 

Silver wire. 42000 

Steel wire, max... . 460000 

Steel, nickel. 250000 

Steel piano wire . 325000-390000 

Tin, drawn. 4000-5000 

Zinc, cast. 7000-13000 

Zinc, drawn. 22000-30000 


TABLE 7 
Sines of Angles 


Degree 

Sine 

Degree 

Sine 

Degree 

Sine 

Degree 

Sine 

1 

0.017 

24 

0.407 

47 

0.731 

70 

0.940 

2 

0.035 

25 

0.423 

48 

0.743 

71 

0.946 

3 

0.052 

28 

0.438 

49 

0.755 

72 

0J951 

4 

0.070 

27 

0.454 

50 

0.766 

73 

0.956 

5 

0.087 

28 

0.469 

51 

0.777 

74 

0.961 

6 

0.105 

29 

0.485 

52 

0.788 

75 

0.966 

7 

0.122 

30 

0.500 

53 

0.799 

76 

0.970 

8 

0.139 

31 

0.515 

54 

0.809 

77 

0.974 

9 

0.158 

32 

0.530 

55 

0.819 

78 

0.978 

10 

0.174 

33 

0.545 

56 

0.829 

79 

0.982 

11 

0.191 

34 

0.559 

57 

0.839 

80 

0.985 

12 

0.208 

35 

0.574 

58 

0.848 

81 

0.988 

13 

0.225 

36 

0.588 

59 

0.857 

82 

0.990 

14 

0.242 

37 

0.602 

60 

0.866 

83 

0.993 

15 

0.259 

38 

0.616 

61 

0.875 

84 

0.995 

16 

0.276 

39 

0.629 

62 

0.883 

85 

0.996 

17 

0.292 

40 

0.643 

63 

0.891 

86 

0.998 

18 

0.309 

41 

0.656 

64 

0.899 

87 

0.999 

19 

0.326 

42 

0.669 

65 

0.906 

88 

0.999 

20 

0.342 

43 

0.682 

66 

0:914 

89 

0.999 

21 

0.358 

44 

0.695 

67 

0.921 

90 

1.000 

22 

0.375 

45 

0.707 

68 

0.927 



23 

0.391 

46 

0.719 

69 

0.934 





TABLE 8 




Indices of Refraction 


Air. 

1.000294 

Glass, crown. 

.. . 1.53 

Alcohol. 

1.36 

Glass, flint. 

. . . 1.60 

Benzine. 

1.49 

Glycerine. 

. . . 1.47 

Carbon disulphide 

1.68 

Ice. 

. . . 1.31 

Diamond. 

2.47 

Turpentine. 

. . . 1.48 

Ether. 

1.36 

Water. 

. . . 1.34 


174 






















TABLE 9 



Melting Point — 

Degrees Centigrade 


Aluminum.. 

. 657 

Nickel. 

.. 1452 

Carbon. 

. Infusible 

Platinum. 

.. 1760 

Copper. 

. 1065 

Silicon. 

. 1200 

Gold. 

. 1071 

Silver. 

. . 961 

Iron, pure. . 

. 1550 

Sulphur. 

. . 114.5 

Lead. 

. 327 

Tin. 

... 232 

Mercury. . . 

. -38.85 

Zinc. 

.. 419 


TABLE 10 


Boiling Point — Degrees Centigrade 


Alcohol, ethyl. 

. . 78.3 

Ether. 

. 34.6 

Alcohol, wood. 

. . 64.7 

Gasoline. 

. 70-90. 

Acetic acid. 

. . 118. 

Glycerine. 

. 291. 

Ammonia. 

.. -38.5 

Mercury. 

. 357. 

Benzene. 

. . 80. 

Sulphur. 

. 444.7 

Bisulphide of carbon. . . . 

. . 46.2 

Turpentine. 

. 159. 

Chloroform. 

. . . 61.2 

Water. 

. 100. 


TABLE 11 


Coefficients of 

Aluminum. . . 

Brass. 

Bronze. 

Copper. 

Glass, tube. . 

Gold. 

Iron, cast.... 

Iron, wrought 


Linear Expansion 


Lead. 0.0000280 

Marble. 0.0000079 

Pine. 0.0000050 

Platinum. 0.0000089 

Silver. 0.0000194 

Steel, tempered. 0.0000132 

Tin. 0.0000230 

Zinc. 0.0000298 


0.0000222 

0.0000188 

0.0000184 

0.0000187 

0.0000083 

0.0000146 

0.0000113 

0.0000122 


TABLE 12 
Specific Heats 


Aluminum. 0.2185 

Brass. 0.0940 

Copper. 0.0933 

German silver. 0.0946 

Glass. 0.1900 

Gold. 0.0320 

Ice. 0.5040 

Iron. 0.1125 


Lead. 

. 0.0315 

Mercury. 

. 0.0335 

Nickel. 

. 0.1100 

Platinum. 

. 0.0320 

Quartz. 

. 0.1910 

Silver. 

. 0.0559 

Tin . 

. 0.0559 

Zinc. 

. 0.0935 


175 






























































TABLE 13 


Specific Resistance 


Aluminum. 18.7 

Copper, annealed. 10.45 

Copper, hard. 10.65 

German silver. 181.0 

Iron. 64.0 

Iron, annealed. 90.0 


Ohms per Mil-Foot 

Lead. 120.3 

Mercury. 58.2 

Manganin. 250-450. 

Platinum. 59.0 

Silver. 9.8 


TABLE 14 

Diameter of Wires, American Wire Gauge (B. & S.) 


Gauge 

Diameter 

Diameter 

No. 

Mils 

Mm. 

0000 

460.0 

11.68 

000 

409.6 

10.40 

00 

364.8 

9.266 

0 

324.9 

8.252 

1 

289.3 

7.348 

2 

257.6 

6.544 

3 

229.4 

5.827 

4 

204.3 

5.189 

5 

181.9 

4.621 

6 

162.0 

4.115 

7 

144.3 

3.665 

8 

128.5 

3.264 

9 

114.4 

2.906 

10 

101.9 

2.588 

11 

90.74 

2.305 

12 

80.81 

2.058 

13 

71.96 

1.828 

14 

64.08 

1.628 

15 

57.07 

1.450 

16 

50.82 

1.291 

17 

45.26 

1.150 

18 

40.30 

1.024 


Gauge 

Diameter 

Diameter 

No. 

Mils 

Mm. 

19 

35.39 

0.912 

20 

31.96 

.812 

21 

28.45 

.723 

22 

25.35 

.644 

23 

22.57 

.573 

24 

20.10 

.511 

25 

17.90 

.455 

26 

15.94 

.405 

27 

14.20 

.360 

28 

12.64 

.321 

29 

11.26 

.286 

30 

10.03 

.255 

31 

8.93 

.227 

32 

7.95 

.202 

33 

7.08 

.180 

34 

6.30 

.160 

35 

5.61 

.143 

36 

5.00 

.127 

37 

4.45 

.113 

38 

3.96 

.101 

39 

3.53 

.089 

40 

3.15 

.079 


Lb □ '3 


176 













Specifications — Automobile Engines — 1931 


Make and 

Cylinders 

Bore and 

Cylinder Tax. 

Max. H.P. 

Model 

and Head 

Stroke 

Disp. 

H.P. 

and R.P.M. 

Auburn 

8-98 

8—L 

3 x 4f 

267 

28.8 

98 @ 3400 

Austin 


4-L 

2.2x2 

46 

7.8 

14 @ 3200 

Buick 

8-50 

8-1 

2f x4| 

221 

26.5 

77 @ 3200 

Buick 

8-60 

8-1 

x 4f 

273 

30.0 

90 @ 3000 

Cadillac 

V-16 

16-1 

3 x.4 

452 

57.5 

165 @ 3400 

Chevrolet 


6-1 

3 t \ x 3f 

194 

26.3 

50 @ 2900 

Chrysler 

6 

6-L 

3|x4i 

196 

23.4 

62 @ 3200 

Chrysler 

70 

6-L 

3f x 5 

268 

27.3 

93 @ 3200 

Chrysler 

Imp. 

8-L 

3§ x 5 

385 

39.2 

125 @ 3200 

Cord 


8-L 

31 x 41 

297 

33.8 

125 @ 3600 

De Soto 

6 

6-L 

31x41 

205 

25.4 

67 @ 3200 

Dodge 

6 

6-L 

31 x 41 

212 

25.4 

68 @ 3400 

Dodge 

8 

8-L 

3x41 

240 

28.8 

84 @ 3400 

Durant ] 

6-14 

6-L 

31x4 

199 

25.4 

70 @ 3100 

Elcar 

7 5-A 

6-L 

21 x 4f 

185 

19.8 

61 @ 3000 

Essex Super. 

6-L 

21x41 

175 

19.8 

61 @ 3400 

Ford 

A 

4-L 

31x41 

205 

24.0 

39 @ 2200 

Franklin 

15 

6-1 

31 x 4f 

274 

29.4 

87 @ 3000 

Graham 

Spec. 

6-L 

31x41 

224 

25.4 

76 @ 3400 

Gardner 

136 

6-L 

21 x 4f 

185 

19.8 

70 @ 3500 

Hudson 


8-L 

21x41 

234 

26.5 

87 @ 3600 

Hupmobile 

C 

6-L 

31x41 

212 

25.4 

70 @ 3200 

Hupmobile 

: C 

8-L 

21 x 4f 

240 

26.5 

90 @ 3200 

Jordan 

80 

8-L 

21 x 4f 

247 

26.5 

80 @ 3000 

Kissel 

73 

6-L 

21 x 4f 

185 

19.8 

70 @ 3500 

Lincoln 


8-L 

31x5 

384 

39.2 

120 @ 2900 

Marmon 

70 

8-L 

2Hx41 

211 

25.4 

81 @ 3400 

Nash 

6-60 

6-L 

31 x 4f 

201 

23.4 

60 @ 2800 

Nash 

8-80 

8-1 

3x41 

240 

28.8 

86 @ 3200 

Oakland 

8 

8-L 

3tV x 3| 

251 

37.8 

85 @ 3200 

Oldsmobile 

6-L 

3^ x 41 

198 

24.4 

65 @ 3350 

Packard 

826 

8-L 

3^x5 

320 

32.5 

100 @ 3200 

Peerless Mast. 

8-L 

3f x 41 

322 

36.5 

120 @ 3200 

Pierce Arrow 

8-L 

3!x4f 

366 

39.2 

125 @ 3000 

Plymouth 

Pontiac 


4-L 

6-L 

3f x4f 
3i% x 31 

196 

200 

21.0 

26.3 

48 @ 2800 
60 @ 3000 


177 


Specifications — Automobile Engines —1931 ( Cord .) 


Make and 

Cylinders 

Bore and 

Cylinder 

Tax. 

Max. H.P. 

Model 

and Head 

Stroke 

Disp. 

H.P. 

and R.P.M. 

Reo 20 

6-L 

3f x 5 

268 

27.3 

85 @ 3200 

Reo 30 

8-L 

3| x 5 

356 

36.5 

125 @ 3300 

Studebaker 

6-L 

31 x 4| 

205 

25.4 

70 @ 3200 

Studebaker D. 

8-L 

3tV x 

221 

30.0 

78 @ 3400 

Studebaker C. 

8-L 

x 41 

250 

30.0 

101 @ 3200 

Stutz LA. 

6-0 

3| x 41 

242 

27.3 

85 @ 3150 

Willy s 6-97 

6-L 

31x3| 

193 

25.4 

65 @ 3400 

Willys 8-80 

8—L 

31x4 

245 

31.3 

80 @ 3200 

Willys-Knight 

6-S 

3f x 4f 

255 

27.3 

87 @ 3200 


Specifications — Automobile Chassis — 1931 


Make and 
Model 

Wheel 

Base 

In. 

Size 

Rim 

Tire 

Gear 

Ratio 

High 

Transmission 
Ratios * 

2nd Low Rev. 

Weight 

4-D 

Sedan 

Auburn 

8-98 

126 

17-6.00 

4.45 

1.68 

2.87 

3.76 

3590 

Austin 


75 

18-3.75 

5.25 

1.73 

3.13 

3.84 

1130 

Buick 

8-50 

114 

18-5.25 

4.55 

1.75 

3.00 

3.86 

3170 

Buick 

8-60 

118 

19-5.50 

4.45 

1.75 

3.03 

3.65 

3795 

Cadillac 

V-16 

148 

19-7.00 

4.39 

1.51 

2.50 

3.00 

5850 

Chevrolet 

109 

19-4.75 

4.10 

1.77 

3.32 

4.20 

2685 

Chrysler 

6 

116 

19-5.00 

4.66 

1.82 

3.04 

3.65 

2695 

Chrysler 

70 

118 

18-5.50 

3.82 

2.19 

3.38 

3.49 

3590 

Chrysler 

Imp. 

145 

18-7.50 

3.82 

3.82 

2.35 

3.38 

4705 

Cord 


137^ 

18-7.00 

4.80 

1.68 

2.84 

3.45 

4705 

De Soto 

6 

113 

19-4.75 

4.33 

1.79 

2.76 

3.44 

2705 

Dodge 

6 

114 

19-5.00 

4.66 

1.79 

2.76 

3.44 

3040 

Dodge 

8 

118 

18-5.50 

4.60 

1.79 

2.75 

3.44 

3340 

Durant 

6-14 

112 

19-5.00 

4.40 

1.77 

3.32 

4.20 

2790 

Elcar 

75-A 

117 

19-5.00 

4.90 

1.77 

3.07 

4.00 

2940 

Essex 

Super 

113 

19-5.00 

5.40 

1.96 

3.24 

4.17 

2805 

Ford 

A 

103| 

19-4.75 

3.77 

1.85 

3.13 

3.75 

2462 

Franklin 

15 

125 

19-6.50 

4.73 

2.41 

3.55 

3.21 

4220 

Graham 

Spec. 

115 

18-5.50 

4.10 

2.41 

3.54 

3.10 

3150 

Gardner 

136 

122 

19-5.50 

4.45 

2.32 

3.75 

3.20 

3250 

Hudson 


119 

18-5.50 

4.63 

1.92 

2.91 

3.45 

3550 


* To obtain final gear ratios multiply ratio in high by transmission 
ratio. 


178 


Specifications — Automobile Chassis— 1931 ( Cont .) 


Make and 
Model 

Wheel 

Base 

Size 

Rim 

Gear 

Ratio 

Transmission 
Ratios * 

Weight 

4-D 

In. 

Tire 

High 

2nd 

Low 

Rev. 

Sedan 

Hupmobile 6-C 

113| 

19-5.50 

4.70 

1.65 

2.87 

3.44 

2905 

Hupmobile 8-C 

118 

19-5.50 

4.55 

1.68 

2.87 

3.76 

3175 

Jordan 80 

120 

18-5.50 

4.90 

1.82 

3.43 

3.64 

3590 

Kissel 73 

117 

18-6.00 

4.89 

1.69 

3.11 

4.10 

3212 

Lincoln 

145 

19-7.00 

4.58 

1.76 

3.08 

3.66 

4790 

Marmon 70 

1121 

19-5.50 

4.90 

1.83 

3.04 

3.65 

3833 

Nash 6-60 

114| 

19-5.00 

5.10 

1.75 

3.06 

3.77 

2800 

Nash 8-80 

121 

18-5.50 

4.45 

1.69 

3.08 

4.17 

3360 

Oakland 8 

117 

18-5.50 

4.55 

1.63 

3.06 

3.44 

3140 

Oldsmobile 

113* 

18-5.25 

4.56 

1.63 

3.06 

3.44 

2950 

Packard 826 

127* 

19-6.50 

4.69 

1.84 

3.14 

2.54 

4479 

Peerless Mast. 

125 

19-6.00 

4.45 

2.46 

4.01 

3.46 

4521 

Pierce Arrow 

134 

19-6.50 

4.42 

2.08 

3.12 

2.72 

4523 

Plymouth 

110 

19-4.75 

4.38 

1.79 

2.75 

3.44 

2565 

Pontiac 

112 

19-5.00 

4.55 

1.77 

3.32 

4.21 

2705 

Reo 20 

120 

18-6.00 

4.07 

1.67 

3.13 

3.81 

3700 

Reo 30 

130 

18-6.50 

3.77 

1.38 

2.29 

2.84 

4305 

Studebaker 6 

114 

19-5.25 

4.73 

1.82 

3.22 

3.65 

2950 

Studebaker D. 

114 

19-5.25 

4.73 

1.82 

3.22 

3.65 

3155 

Studebaker C. 

124 

19-6.00 

4.73 

1.68 

2.87 

3.76 

3520 

Stutz LA. 

127* 

19-6.00 

4.75 

1.68 

2.87 

3.76 

4200 

Willys 6-97 

110 

19-5.00 

4.60 

1.53 

2.70 

3.33 

2682 

Willys 8-80 

121 

19-5.50 

4.40 

1.75 

3.06 

3.76 

3303 

Willys-Knight 

121 

18-6.00 

4.18 

1.75 

3.06 

3.76 

3582 


* To obtain final gear ratios multiply ratio in high by transmission 
ratio. 


179 


Horsepower of Automobile Engines at Different Speeds 


Make and 


No. of 


H.P. at given R.P.M. Maximum 


Model 

Cylinders 

600 

1200 

1800 

2400 

3000 

R.P.M. 

Auburn 8-98 

8-L 

20.0 

41.0 

61.5 

81.2 

92.5 

98 @ 3400 

Buick 8-50 

8-1 

16.4 

35.5 

53.0 

67.8 

76.0 

77 @ 3200 

Buick 8-60 

8-1 

21.0 

45.0 

68.5 

85.0 

90.0 

90 @ 3000 

Cadillac V-16 

16-1 

35.0 

72.0 

104.0 

134.0 

157.0 

165 @ 3400 

Chevrolet 

6-1 

13.7 

27.5 

41.2 

49.0 


50 @ 2900 

Chrysler 

6-L 

13.5 

28.2 

41.0 

53.2 

61.0 

62 @ 3200 

Chrysler Imp. 

8-L 

28.0 

59.5 

89.0 

113.0 

123.0 

125 @ 3200 

Dodge 

6-L 

14.0 

30.0 

46.0 

59.0 

67.0 

68 @ 3400 

Dodge 

8-L 

17.0 

37.0 

54.0 

68.0 

78.0 

84 @ 3400 

Durant 6-14 

6-L 

15.0 

31.5 

46.5 

59.5 

69.5 

70 @ 3100 

Essex 

6-L 

13.0 

27.0 

40.5 

50.5 

58.5 

61 @ 3400 

Ford A 

4-L 

13.5 

28.5 

35.0 



39 @ 2200 

Franklin 15 

6-1 

20.0 

40.0 

68.0 

80.0 

87.0 

87 @ 3000 

Graham Spec. 

6-L 

16.0 

34.0 

51.0 

66.0 

74.0 

76 @ 3400 

Hudson 

8-L 

17.5 

36.5 

52.5 

67.5 

80.0 

87 @ 3600 

Marmon 70 

8-L 

16.0 

35.0 

52.5 

67.0 

77.0 

81 @ 3400 

Nash 8-80 

8—L 

18.5 

36.5 

54.6 

73.0 

85.0 

86 @ 3200 

Oakland 

8-L 

18.0 

40.0 

58.0 

77.0 

82.0 

85 @ 3200 

Oldsmobile 

6-L 

14.0 

29.0 

44.0 

57.5 

64.0 

65 @ 3350 

Pontiac 

6-L 

14.0 

32.0 

45.0 

56.0 

60.0 

60 @ 3000 

Reo 20 

6-L 

20.0 

39.0 

59.0 

75.0 

84.0 

85 @ 3200 

Reo 30 

8-L 

26.0 

52.0 

78.0 

100.0 

122.0 

125 @ 3300 

Studebaker Six 

6-L 

14.0 

30.5 

45.0 

58.0 

68.0 

70 @ 3200 

Studebaker Diet. 8-L 

15.5 

34.5 

52.0 

68.0 

75.0 

78 @ 3400 


180 




APPENDIX B 

A Suggested List of Apparatus for the Experiments 

Experi¬ 

ment 

1 Rectangular block, 2 x 4 x 16 inches. A half-meter stick. 

2 Vernier caliper. Brass cylinder (200-gram mass). 

3 Micrometer screw. Steel ball, diameter half-inch. 

4 Spring balance, 18 oz. capacity, and light pan. Rectangular 
block, 2x2x4 inches. Catch bucket of overflow apparatus. 
Support rod, two V-clamps, and seven-inch spike. 

5 Harvard trip balance. Block of weights, 1 gm.-500gm. Block 
and bucket of Experiment 4. 

6 Support rod, clamp, and spike. Spring balance, 64 oz. Two- 
pound and four-pound masses. Half-meter stick with holes 
at 10, 25, and 49. 

7 Support rod, clamp, and small cross rod. Two spring balances. 
One-, two-, and four-pound masses. Half-meter stick. 

8 Trip balance. Small wood prism. Half-meter stick. Block 
of weights. Small cylinder of unknown weight. 

9 Support rod, two clamps, spike. Two spring balances, 64 oz. 
capacity. Two single pulleys. Four-pound mass. 

10 Trip balance. Inclined-plane apparatus. Meter stick. Block 
of weights. (Hall-carriage and spring balance) 

11 Automobile jack, screw type (Walker 216B). Support rod, 
clamp, and spike. Spring balance, 64 oz. capacity. Spring 
balance, 30 lb. capacity. Small cylinder. Lever, 1 x 2 x 18 
inches. Table clamp. 

12 Grooved wheel with handle (wheel of rotovac pump). For 
axle, cut two inches from the threaded end of a 19 mm. support 
rod. Place axle in receptacle in table top or in a tripod base 
clamped to table. Two spring balances, 30 lb. capacity. (64 oz. 
balance may be used for one.) Two table clamps. Three feet 
of one-fourth inch rope. 

13 Pine board 1 x 6 x 18 inches. Pine block, 2x4x5 inches 
with screw eye in end. Spring balance, 64 oz. Two- and four- 
pound masses. Sandpaper. 

14 Board and block of Experiment 13. Two- and four-pound 
masses. Spring balance, 64 oz. Support rod and clamp. A 
spike driven in the edge of the board near one end serves as a 
means of clamping the board at any height. 

181 


Experi¬ 
ment % 

15 Support rod, clamp and spike. Spring balance, 18 oz., and 
light pan. Six-inch battery jar. Overflow can and bucket. 
A sinking block and a floating cylinder. 

16 Apparatus of Experiment 15. Large specimens of brick, 
cannel coal, stone, etc. 

17 Support rod and clamp. Burette clamp. U-tube about eight 
inches long. Rubber tubing. Half-meter stick. 

18 A closed manometer about one foot long. Other apparatus as 
in Experiment 17. 

19 Support rod and clamp. Meter stick and light pan. Half¬ 
meter stick. Block of weights. A right-angle clamp with a 
19 mm. V-opening may be used to clamp the meter stick in a 
horizontal position. 

20 Table clamp. Spring balance, 30 lb. Spike. Micrometer screw. 
Copper wire No. 26. Iron and brass wire No. 32. 

21 Three spring balances, 64 oz. Connecting cords. Blocks with 
hooks and table clamps. Compass and protractor. 

22 Support rod, two V-clamps and spike. Two spring balances, 
64 oz. A two-pound mass. Half-meter stick with hole near 
one end and screw eye in other end. Compass and protractor. 

23 Support rod and clamp. Board and block of Experiment 13. 
Four-pound mass. Compass and protractor. Spring balance, 
64 oz. 

24 Grooved plank, five feet long. Heavy ball and lycopodium 
powder. For a powder sifter place three layers of cheesecloth 
over wide-mouth bottle. Meter stick and a half-meter stick. 
Blocks of Experiment 1. The plank should have a guide, or 
a vertical surface extending from edge to within three-quarters 
of an inch of the center of groove, for releasing the ball. 

25 Support rod and p ndulum clamp. Fine silk cord. One and 
one-half inch iron and wood balls. Meter stick. Watch. 

26 A nine- or ten-foot pendulum. Use fine steel or brass wire and 
a two- or four-pound mass for bob. Meter stick or tape. Stop 
watch. 

27 Apparatus the same as in Experiment 24. 

28 Support rod, right-angle clamp, and a large universal clamp. 
Glass tube, 45 cm. length and 4 cm. diameter. Hydrometer 
jar, size 2 x 12 inches. Tuning fork, 256 vibrations. 

182 


Experi¬ 

ment 

29 Two support rods, two right-angle clamps, and two burette 
clamps. Three-inch glass funnel and two Y-tubes. Two heavy 
wall tubes, 3 in. and 30 in. Three light wall tubes, 12, 25, and 
29.5 in. Two tuning forks, 384 and 512 vibrations. 

30 Two table clamps. Spring balance, 30 lb. Piano wires, Nos. 
24 and 26. Small iron ring and washer. Wood prism, 2 in. 
Half-meter stick. Two tuning forks, 384 and 512 vibrations. 

31 Plane mirror, 4 x 15 cm. Two wood blocks. Foot rule. Pins. 

32 Cylindrical mirror, 5 x 10 cm. Rule, pins and compass. 

33 Same as Experiment 32. 

34 Spherical mirror, concave and convex, 12 cm. diameter, 
mounted. Optical bench consisting of support rod, two end 
supports, three index clamps, mounted screen, and gas jet. 

35 Six-inch battery jar. Table clamp. Compass. Protractor. 
Refraction board 1x5x7 inches with small groove sawed 
across one side and the two edges near the center. A small 
hole to fit a lj-in. nail drilled near lower left-hand corner and 
in groove about two inches from left-hand edge. 

36 Glass plate, 7 cm. x 7 cm. x 6 mm., two edges polished and two 
ground. Compass. Protractor. Pins. Rule. 

37 Equilateral glass prism. Compass. Protractor. Pins. Rule. 

38 Optical bench of Experiment 34. Lens holder, mounted. 
Double convex lens, 5 cm. diameter, 12.5 cm. focus. Double 
concave lens, 5 cm. diameter, 20 cm. focus. 

39 Boiling chamber and burner. Linear expansion apparatus 
with micrometer. 

40 Boiling apparatus. Calorimeter. Centigrade thermometer. 
Balls of iron, brass, and iron, 1§ in. Trip balance. Block of 
weights. 

41 Support rod, clamp, and spike. Calorimeter. Thermometer. 
Balance. Weights. Iron ball, f in. Chromel wire, No. 28. 

42 Calorimeter, thermometer, balance, and weights. Snow. 

43 Boiling apparatus. Apparatus of Experiment 42. 

44 Support rod, right-angle clamp, and burette clamp. Tripod 
and burner. Copper boiler or 800 cc. beaker. Thorp gauge. 

45 Two bar magnets, f x 6 in. Magnet board, 9x11 in., with a 
single groove on one side and two grooves 2 in. apart on other 
side. Iron filings and sifter. 

183 


Experi¬ 

ment 



MENT . 

46 Voltmeter, 0-10 range. Student demonstration battery. Five 
different elements and five solutions or electrolytes. 

47 Voltammeter, 0-10 range. Two dry cells. Key. Four feet of 
German-silver wire, No. 30 (wire on Wheatstone bridge may be 
used). Micrometer screw. 

48 Wheatstone bridge. Dry cell. Key. Resistance box. Four 
feet German-silver wire, No. 30. Student galvanometer. 

49 Voltammeter, 0-10 range. Resistance box. Two dry cells 
and key. 

50 Apparatus of Experiment 49. 

51 Apparatus of Experiment 49 with three dry cells. 

52 Apparatus of Experiment 51. 

53 Compass. Large iron nail. Dry cell and key. Block, 2x2x4. 

54 Electric doorbell. Two keys and dry cell. 

55 Telegraph key and sounder combined. Support rod, clamps, 
and wire. 

56 A source of current of 2 or more volts. Student cell with 2 
copper, 2 lead, and 1 carbon electrode. Solutions of copper 
sulphate and sulphuric acid. Salt. 

57 Extension cord with key socket. Support rod, right-angle 
clamp, and burette clamp. Calorimeter and thermometer. 
Balance and weights. 60-watt lamp. 

58 Student galvanometer. Two insulated copper wires, No. 18, 
seven feet and three feet long. Large wire nail. Two bar mag¬ 
nets. Dry cell and key. Three-inch piece of broom handle. 

59 St. Louis motor, improved. A.C. a mature and electromagnet 
attachment. Galvanometer. Resistance box. Dry cell, con¬ 
necting wires and key. 

60 Apparatus of Experiment 58. 

61 Table of Specifications — Automobile Engines. Appendix. 

62 Blue prints of power and torque curves may be secured from 
any automobile manufacturer. 

63 Table of Specifications — Automobile Chassis. Appendix. 

64 The wiring chart of the electric system of any automobile can 
be secured through the Automobile Digest, 22 East 12th St., 
Cincinnati, Ohio. 



184 



















' V 
















































